Compressed Air Guns In installment Part 1 of this series titled Doomsday Self-Defense, Part 1: Rethinking Black Powder, discussed using black powder as a back-up propellant for firearms in the event that conventional ammunition loaded with standard smokeless powder becomes scarce. Yes, conventional smokeless powder is likely to grow scarce if basic infrastructure is out of commission for months or years, so it does make sense for people to think about designing and building firearms that will work with black powder. Black-powder-burning guns were chosen as the first alternative to conventional firearms in this discussion series because black powder is kind of like Spider Man. So, how is black powder like Spider Man? Well, remember kids, Spider Man does whatever a spider can: he spins a web any size — catches crooks just like flies — watch out for Spider Man! So, just as Spider Man does whatever a spider can, black powder can pretty easily fill all of the same job descriptions as smokeless power whenever smokeless powder turns into a deadbeat dad. So, the next logical question would be this: If smokeless powder is such a great problem solver that rides in with trumpets blaring and lively music playing whenever supplies of conventional smokeless powder run dry, then why waste time by discussing any other propellent methods for firearms? In answer to the previous question, yes, we have to admit that black powder makes a great second choice as a prom date whenever conventional smokeless powder is not around; however, just as making good old home-cooked Southern biscuits from basic ingredients requires a bit of time and love, it also takes a bit of time and love to make black powder from scratch. According to the website survival-manual.com, the chief ingredient in pretty much every recipe for home-brewed gun propellant is saltpeter, and the process of making salt peter in-house typically lasts around three months at the very least, provided that the local climate is hot and humid, and the process of procuring saltpeter can take up to a year in a spot that is notably dry or cold. In places like Michigan, the summer is hot and humid, so in the summer time when the living is easy, getting bacteria to turn the nitrates in animal manure into usable potassium nitrate is not too hard. On the other hand, Michigan gets very cold winters, so the cold temperatures in the winter will halt saltpeter production; thus, in colder climates saltpeter production is really a seasonal thing, and that limits supply potential. Given India's year-round steam-bath climate, bottomless supply of cheap labor, and vast quantities of cow manure, it is no surprise that the British eventually saw India as the go-to spot for obtaining the huge quantities of saltpeter they needed to keep their subjects so loyal.

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So, there you have it, black powder has many nice qualities, and yes, it can be made in-house with some wood ash, urine, manure, and a bit of plant matter, but the problem is time; namely, making black powder simply takes too long. Yes, one decent-sized farm can make hundreds of pounds of saltpeter per year, and although the task of making saltpeter is nowhere near as involved as that of producing smokeless powder, the process of making saltpeter still takes a little bit of know-how and a fair amount of patience. As a point of refence, the Foxfire series of books dedicates a section of their repository of information about Appalachian back-woods wisdom to a discussion about making gunpowder on a homestead. Foxfire's section on making gunpowder says that old Uncle Elmer can get about one pound of good possum-shooting black powder for his musket every three months by digging-up the soil in his backyard chicken coup and milking it for saltpeter. So, the basic run-down on the speed of saltpeter production adds up to one backyard chicken coup being able to produce about four pounds of gunpowder per year. Having a chicken coup that produces about four pounds of good-quality black powder per year is fine if you live back up-the-holler off Copperhead road in the hills of Kentucky, and making four pounds of down-home gunpowder per year is fine if you are just using your homemade propellant to hunt. On the other hand, for larger-scale campaigns of self-defense, like defending a county-sized area, supplies of black powder could very easily get scarce under prolonged conflict, right along with supplies of smokeless powder. When looking at historical records, since the concept of firearms first arrived in a meaningful way, and before the mass adoption of smokeless powder, wars and periods of protracted conflict were always accompanied by troubling concerns about shortages of saltpeter. For example, during the American Revolutionary War, the colonial army led by General George Washington was so short on saltpeter supplies that they had to pay blockade-runners to use their light, fast, and shallow-drafted sailing ships to bring this precious powder in from the British Virgin Islands at a very high cost, or else the Continental Army of George Washington would be forced to surrender to the British1. Although not every army fighting a war back in the days when black powder ruled the roost faced shortages of saltpeter; none the less, running out of saltpeter and not being forced to wait months for a new supply to emerge was a constant concern. Not surprisingly, soon after the American Civil War started, the Confederate government set-up a special depart called the Niter Bureau on April 1, 1862; and the sole mission of the old stars-and-bars Niter Bureau was to ensure a continual supply of saltpeter for the Confederate army. The Confederacy managed to avoid running-out of gunpowder by creating a decentralized network of small saltpeter production facilities along with a decentralized distribution network; however, a huge amount of industrial capacity and manpower had to be sacrificed from the war effort just to keeping the supply lines of saltpeter flowing2.

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The saltpeter must flow. Image courtesy of nme.com Creating a decentralized production and distribution network for black powder is also important because relying on large centralized powder mills will create supply vulnerabilities. Moreover, relying on centralized production of black powder is never a good idea because finding the locations of large powder-making facilities is not too hard given the huge buildings required and the large workforces needed to operate these facilities; plus, destroying these large plants will always be a high priority for the bad guys.

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The end results of getting disarmed. Image courtesy of pictureflip.com So, yes, it is possible to maintain a sufficient flow of saltpeter even when times are tough, but advanced planning and preemptive infrastructure building are necessary to keep saltpeter supplies flowing, and getting the finished product to the places where it is needed can also be a problem, so a solid and redundant distribution network has to be built alongside the production infrastructure. Given the time needed to produce saltpeter from scratch, and given the time needed to build a robust saltpeter production base and distribution network, it would be best for people to start developing the needed saltpeter production networks and infrastructure right away. Considering the lag in production time associated with making saltpeter, as well as the need to have an effective means to distribute the finished product, it would also be wise for people to have a backup plan if — or when — black powder supplies get tight. In light of black powder's slow and cumbersome production process, firearms powered by compressed air are worth considering as a compliment, or even as a parallel back-up plan, to black-powder-driven firearms when things get tough and conventional ammunition is scarce, and this is the case for a few reasons. The first reason that compressed air-based firearms should be given serious consideration as self-defense appliances because they are effective. At this time, the most effective compressed

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air guns are long-range air-powered sniper rifles. The truth is, the compressed-air-powered hunting rifles sold on the civilian market work well as sniper rifles, plus they offer a few immediate and practical advantages over their powder-driven rivals, which makes a good case for choosing these rifles even when conventional smokeless-powder-burning sniper rifles are readily available. The second reason air guns should be valued as a technology of self-defense is because they require no propellant other than the air that is almost always surrounds us.

The image shown above is included to provide a sample image of a modern air rifle that is sold to the hunting market, yet a rifle like the one seen above could easily be repurposed as a sniper rifle. The rifle pictured above does not have the optimal design for long-range shooting, but it is still a capable long-range rifle. Image courtesy of rpsolutions.nl

A little History of Air Guns

True, many of us had BB guns as toys when we were kids, and most people still imagine compressed air guns to be nothing more than implements of animal cruelty that naughty little boys use to inflict undue suffering and loss of life on poor backyard-dwelling fauna like squirrels, lizards, and small birds. Indeed, plenty of smaller air guns definitely fit this description, but larger air guns that are able to abrupt even the largest, meanest, smelliest, most bellowing, and most-snortin of animals certainly do exist, and these big hairy-chested specimens of gassy gun bravado have actually been around for a while. As listed on Wikipedia, the earliest known air gun is powered by a steel spring and leather bellows and dates from 1580. This earliest of known air rifles is on display at the Livrustkammaren Museum in Stockholm, Sweden; and references to large caliber and small-bore air rifles can be found from many parts of Europe over the centuries3. Early air rifles were difficult to produce with the materials technology of that era, and they were more mechanically complex than their gunpowder-driven peers, so these devices were primarily a provenance of the aristocracy.

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Many early air rifles were rather small, and many early air guns were also used primarily for indoor recreational shooting. Additionally, most of these small indoor-shooting air rifles from the age of quill pens, along with the air-driven pistols of those days, were powered by leather bellows that were compressed by springs. By contrast, even as early as the 1600s, large .30-caliber to .51-caliber rifles with metal air tanks that were able to take-down game as large as deer and wild boar were also around. Early big-bore air rifles were expensive because they required a level of workmanship similar to that required to make fine clocks of the same era. Early air guns were all unique, and each early air rifle was a work of art on account of these guns needing precise springs, tight part clearances, smooth metal surfaces, and good airtight seals on their tanks in order to function. The earliest big-bore hunting rifles were also luxury items of the idle rich because they required a manservant of his lordship to strain with a single-stage pump for about an hour in order to provide enough juice for a single pig-killing shot.

The image above shows a classic English air rifle from the 1800's. Image courtesy of forum.vintageairgunsgallery.com

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The Japanese also got into the business of making expensive luxury air guns for the wealthy in the first decade of the 19th century. Image courtesy of metmuseum.org Despite basically functioning as toys for the wealthy, old-time compressed air rifles even saw a bit of military service in the late 18th century. The Girandoni air rifle was the only know air rifle to have ever been pressed into military service, and this type of rifle was invented by a Tyrolean named Bartholomäus Girandoni. Girandoni's rifles were officially in service in the Austrian Empire from 1780 until 1815, and they offered many nice advantages. Despite their nice feature, Girandoni rifles ultimately fell out of favor because of their high production cost, lengthy production times, and their constant need for maintenance. For example, the gaskets in Girandoni's rifles were made of oil-saturated leather, so the gaskets on these rifles had to be continuously oiled and replaced or else these rifles would not work. In addition to constantly needing to keep the leather gaskets of his rifle oiled, any solider who was issued a Girandoni rifle also had to constantly keep the internal mechanical parts of his firearm oiled and clean. Aside from other maintenance issues, the compressed-air reservoirs on Girandoni's rifles were made from pounded sheets of iron that were rived together then braised with brass. Girandoni rifles were braised with brass in order to ensure an airtight seal, so the air reservoirs on Girandoni rifles did hold air, but they were troublingly prone to developing leaks. Not only were the air reservoirs in Girandoni's rifles prone to slowly losing air, they were also known to spontaneously explode on occasion and cause serious injuries, or even death, to their users. The air reservoirs attached to Girandoni rifles also ran the risk of exploding if there was a very

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rapid rise in temperature; for instance, events such as filling the air tank in a cool cellar and then bringing into the sun on a hot day would create a dangerous risk of an air tank explosion.

The image above shows a Girandoni Air Rifle on auction from the Rock Island Auction Company. Image courtesy of rockislandacutions.com Despite seeing a successful, but rather brief, run of military use, big-bore air rifles declined in popularity over the following decades because black-powder-filled cartridges offered powerful rifles that lacked the high cost and reliability problems associated with compressed air rifles. Despite a steady decline in popularity, a small number of expensive high-end air rifles remained in production until the 1920's in various parts of Europe; however, after the introduction of black powder cartridges, compressed air rifles remained in use, but only as hobby shooters and toys for errant boys. Despite remaining in use into the 20th century, two factors greatly reduced the popularity of big-bore air rifles. First, the wide-spread introduction of brass bullet casings filled with black powder arrived, and this created a real decline in the demand for air guns. Next, the mass arrival of brass bullet casings filled with smokeless powder happened, so the effects of these two successive technical innovations meant that interest in using air rifles for military applications or hunting large animals almost completely disappeared until the early 1990s. Despite their drawbacks, the nobility in previous centuries loved to hunt with big bore air rifles because these expensive toys offered some advantages over their powder-driven competitors. The advantages of air guns in the realm of hunting included perks such as producing less noise, having less recoil, being less affected by rain or moisture (flintlock rifles were notorious for not working in the rain), and producing no clouds of smoke. From the military perspective of the 1700s, compressed air rifles offered all of the advantages that made them popular hunting rifles for the nobility, except compressed air guns also offered the advantage of not having a muzzle flash that would give away a shooter's position in low-light conditions. So, yes, we have established that big bore air rifles are not a new invention, nor a new idea, yet this old technology got a new lease on life in the early years of the 1990s thanks the efforts of Dennis Quackenbush who owns the Quackenbush Air Rifle company which is headquartered Missouri. Quackenbush is a machinist by trade who started his company be making custom air rifles that were inspired by the designs of large air-powered hunting rifles that were used by European aristocracy for several centuries. It seems that Mr. Quackenbush made his

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reproductions of early air-powered hunting rifles as a hobby activity he enjoyed; however, his products eventually acquired a small but dedicated fan club. Quackenbush is credited for catalyzing the renaissance in modern big bore air rifles4, but a few manufacturers in Korea took his lead and began to manufacture larger air rifles capable of turning deer into venison steaks back in the 1990s. Back in the 1990's, a few companies in Korea developed a handful of really big air guns that were capable of knocking-down deer because there were such strict regulations placed on regular firearms. In Korea, air guns became the ticket for all types of hunting because the government saw these pneumatic pellet-pushers as nothing more than toys, or tools for hunting small animals. Additionally, Korean apparatchiks never saw air guns as tools of murder, nor did they see air guns as devices suitable for resisting the government, so big-bore air rifles offered Korean outdoorsmen the prospect of hunting larger game with few legal hassles. Another significant development in the modern big-bore air rifle industry was the founding of the Airforce Air Gun company in Fort Worth, Texas back in 1994. Airforce originally offered lightweight small-bore air rifles made from aluminum that were designed for pest control; however, in 2015,5 the company released the Texan series of big bore air rifles that were capable of producing over 500 foot-pounds of energy and firing large .457 caliber bullets. The development of Texan big-bore air rifles was a significant change because these air-powered rifles offered levels of performance comparable to modern rifles that fire smokeless-powder-filled rounds. Since the release of the Texan series, other air rifle manufactures such as Spain's Gamo Air Guns, have developed less expensive knock-off competitor models, and several companies that provide aftermarket enhancements for Texan rifles, like Lethal Air in Virginia, have sprung up. It should come as no surprise that a ground-breaking design like the Texan series that lends itself to milking the most shooting-power out of a bottle of compressed air would inevitably become a big seller, inspire imitators, and entice entrepreneurs to start companies that sell aftermarket products.

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The two photos posted above show a new factory-stock Airforce Texan .50 caliber rifle fitted with a new carbon fiber tank. If an aftermarket 4500-psi air tank is fitted to the rifle pictured above, then the foot-pounds of energy produced by this rifle will climb to 1200+. Images courtesy of airforceairguns.com

Imitation is the highest form of flattery, so it comes as no surprise that other manufacturers are going to copy the basic design of Airforce's line of Texan big-bore air rifles because a good design speaks for itself. The Gamo .45-caliber air rifle seen above is a bit cheaper than a Texan, but it also delivers less power. Image courtesy of pyramidair.com

The Capabilities of Modern Big Bore Air Rifles

When discussing the capabilities of modern air rifles, and comparing them to their smokeless-powder-driven peers, it is vitally important it understand the basic numbers used to evaluate the performance of firearms. An in-depth discussion about ballistics numbers never took place in the previous article about black powder, but that is because there was a lot less need to bring-up ballistics numbers when discussing black powder. The first measure used to evaluate a firearm's actual destructive capability is the term "Foot Pounds" or "Joules". Joules are a metric-based unit used to measure energy in engineering and physics calculations, and Foot Pounds is an English, or Imperial, measurement used to perform

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the same function. As a point of reference, the website for Eclipse Defense, which is a Seattle-based manufacturer of less-than-lethal air guns, says that the American Government's Bureau of Alcohol Tobacco & Firearms considers any projectile that produces 200 or more Joules of energy, or about 153 foot-pounds, to be lethal from a legal standpoint. Another common measure for evaluating firearms is "Feet-Per-Second" or "FPS", which is used to measure the traveling speed of bullets. Lastly, as listed on asknumbers.com, one grain equals .64 grams, and Grains are the unit of measurement used to gage the weight of bullets. Joules can be converted into Imperial Foot Pounds by multiplying the number of Joules a projectile produces by .737 Conversely, Foot Pounds can be converted to Joules by multiplying a measurement given in Foot Pounds by 1.3 To provide a frame of reference, the website ballistics101.com has furnished the ballistics numbers for the following list of bullets: The average foot-pound rating for a 45 ACP pistol round is 411, with an average speed of between 800 and 1000 feet-per-second; depending on the manufacturer of the ammunition. A 357-magnum round produces 500—700 foot-pounds with muzzle velocities that vary between 1200 to 1600 feet-per-second. A 5.56mm AR-15 round is listed as producing between 1200—1600 foot-pounds of energy and moves between 3100 and 3500 feet-per-second; once again, depending on the manufacturer. A standard 7.62 X 39mm round, like those fired by AK-47s, produces between 1400—1600 Foot pounds on average and travel at around 2300 feet-per-second; again, depending on the manufacturer. The weight of a 45 ACP pistol round typically varies between 180 to 220 grains, and a 357-magnum round typically has a grain-weight of around 150. A 7.62 x 39mm round spit-out by and Ak-47 typically weighs-in at around 120 grains; conversely, AR-15 rounds tip the scales between 40 and 70 grains. So, basically, common assault rifles that fire conventional smokeless-powder-driven projectiles are shooting relatively small chunks of metal at high velocities to achieve their killing power. By contrast, a souped-up aftermarket Airforce Texan big-bore air rifle sold by Appalachian Air Guns produces 1210 Foot pounds of energy by driving a 613-grain bullet at 943 feet-per-second. One of the big bad aftermarket Texan air rifles sold by Appalachian Air guns uses air pressured to 4,500-psi to move their lead. Likewise, the company website for Airforce Airguns lists their latest factory-stock 50-caliber air rifle that operates at 3650-psi as producing around 800 foot-pounds of energy. Conversely, the latest factor-stock 50-caiber Texan air rifle gets it swagger by driving 553-grain bullets at around 900 feet-per-second. Airforce's website lists their old factory-standard 45-caliber big-bore rifle that operates at a plebian 3,000-psi as producing around 505 foot-pounds of energy by driving a 405-grain bullet at around 750 feet-per-second. And lest we forget, the Wikipedia entry lists the old Girandoni rifles as having produced a rather measly 117 foot-pounds by driving a 200-grain lead ball at a rather-constipated 500 feet-per-second.

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After reading the previous paragraph, is becomes clear that big-bore air rifles get their gusto by shoving big-old chunks of lead out of their barrels at comparatively low speeds. We can also conclude that a typical big-bore air rifle used for hunting deer, like the 45-caliber Airforce Texan, have about the same ballistic figures as a very powerful handguns, like 357-Magnums; however, some of the larger air rifles pack some serious power. Besides the 50-caliber Texans, other manufactures have tentatively offered some really hard-hitting air rifles. For example, AEA Airguns is a new-kid-on-the-block manufacturer out of China that is still struggling with production issues and low customer satisfaction ratings; however, they do presently offer a 72-caliber air rifle that produces over 1500 foot-pounds of muzzle energy. Unfortunately, AEA's "Zeus" 72-caliber big-bore air rifle is really not well designed, but it does sling bullets as big-around as quarters and produces muzzle energy that is no joke.

The image above shows the host of the YouTube channel called American Airgunner holding the AEA Zeus 72-caliber air gun at AEA's company tradeshow booth. The photo above is a screen capture from a video filmed at the May, 2019 International Air Gun trade show in Las Vegas. Yes, AEA's Zeus is undeniably an absolute monster of a rifle.

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A few other manufacturers have mentioned that they are developing 20mm air rifles that are slated for release which will toss 1750-grain bullets at around 900 feet-per-second. Just for reference, the ballistics numbers mentioned earlier translate to a little over 3,000 foot-pounds of muzzle energy! Just to put the previously stated muzzle energy number in perspective, 3,000 foot-pounds of muzzle energy adds-up to twice the muzzle energy of an AK-47 and around 20-times the official American BATF legal line of lethality; plus, a 20mm compressed air rifle tops all conventional hunting rifles on the market when measuring muzzle energy; except, it packs a bit less spunk than a Winchester 300-Magnum. Yes, a 20mm compressed-air rifle may pack a bit less machismo than the Winchester 300-Magnum, but the Winchester 330-Magum is pretty much the big daddy of all conventional hunting rifles.

The image above is a screen capture showing a portion of a YouTube video where the host of the American Aigunner channel holds an 1100-grain 20mm air rifle bullet. No question, that bullet seen above is a monster of a round, but as far as 20mm air rifle bullets go, the projectile seen above is kind of small. As impressive as the bullet pictured above might seem, some manufacturers of big-bore air rifles are shooting experimental bullets as large as 1750-grains.

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The image above is another screen capture from a video posted on the YouTube channel called American Airgunner. This image is included to show how a 20mm big bore air rifle might appear.

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The image above shows an air rifle enthusiast who built his own experimental 20mm air rifle. This particular rifle wins the blue ribbon for the Biggest Beast of an Air Rifle contest at this-year's county fair. Image courtesy of tirmaillyforum.com

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The image above shows a ballistics chart for the air rifle shown in the image above. Image courtesy of tirmaillyforum.com So, a basic snap-shot of the ballistic capabilities attached to big bore air rifles reveals that they do have the potential to work as stand-ins when conventional bullets are in short supply, and big-bore air rifles will suffice when black powder supply lines are also compromised for whatever reason. As for the issue of shooting at a distance, the newest Texan factory-stock models that are designed to operate with tanks compressed to only 3650-psi can easily hit targets at over 500-yards, and that number arrives without performing any aftermarket upgrades to these rifles. Information gained from a few email message exchanges with manufacturers of souped-up aftermarket Texans revealed that augmented aftermarket 50-caliber Texan air rifles are able to consistently nail targets at 1000+ meters. One of the pearly advantages offered by these really big air guns is furnishing minimal losses of energy for their bullets at long distances. As listed in various forum posts on sniperhide.com and firarmstalk.com, the average sniper shot in an urban area is less than 75 yards, and in war zones outside of congested urban confines, the average sniper shot is still well below 500 meters, so compressed air works just fine as a powerplant for sniper rifles. Yes, very long-ranged sniper shots above 500 meters are taken in areas of conflict, but they are rare, and air rifles are also up to the job when shooters need to make these select long shots. Small bullets that travel at high speeds offer shooters the perk of having very flat bullet arks that require no scope adjustments at shorter ranges, and fast-moving bullets typically require minimal scope adjustments at medium ranges; however, the downside to putting fast little bullets on your payroll is that they lose a lot of energy with distance. The upside to shooting

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large bullets is that they keep their enthusiasm over the course of their walkabouts, but for larger bullets, the trade of to keeping the love over their long strolls through spring meadows is having somewhat droopy sets of ballistics profiles. Basically, the faster a bullet travels, the less drop there will be in its travel trajectory, so bullets that travel at relatively low speeds will have more of an issue with bullet drop than their more-speedy compatriots. Fact is, even shots made with relatively fast-moving bullets fired by conventional smokeless-powder-driven rifles still require scope adjustments to compensate for bullet drop if shooters want to hit any targets at long ranges; however, big-bore air riles need more scope adjustments for long-distance shots on account of their lower bullet speeds. The solution to having droopy travel plans for bullets that sail for long distances is to adjust the scopes on air rifles in order to accommodate this more pronounced bullet trajectory droop. As a way to compensate for the problem of droopy bullet arcs, the manufacturers of hot-rodded aftermarket 50-caliber Texans also sell special mounts for the scopes attached to their rifles in order to permit the steep scope angles shooters must set to compensate for high-levels of bullet trajectory droop. Luckily, even the really big air rifles have fairly flat bullet trajectories that require no scope adjustments if they are shooting under 100—150 yards.

Advantages Offered by Compressed Air Firearms

- Advantage #1. Compressed air firearms have relatively low recoil, even for rifles that hurl very large projectiles. Air rifles move their projectiles by using gas that is at a much lower pressure than that of a smokeless-powder-driven firearm, and even a black-powder-driven gun for that matter, so this low barrel pressure translates to less recoil. The website closefocusreseach.com provides a chart that lists common bullet pressure for conventional smokeless powder driven rounds, and typical barrel pressures for smokeless powder pistols rounds and rifle bullets are between 20,000 and 50,000 psi, which is a whole lot more than the plebian pressure exerted in the barrels of air guns which generally top-out at around 4500-psi. - Advantage #2. Compressed air firearms need to be cleaned a lot less frequently.

If air rifles are filled with clean and dry air, then there will be very minimal reside build-up anywhere inside these guns, which translates to far less need for regular cleaning. Filling a compressed-air firearm with clean and dry air is generally not too hard because fill lines can easily be fitted with inexpensive filters that catch almost all moisture and pretty much every small particle that might enter an air gun's tank.

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- Advantage #3. Compressed air firearms generally use smaller individual units of ammunition.

Compressed air firearms use air stored in external tanks to push their products, so the actual ammunition shoved-out by air guns requires less storage space because no casings filled with power are ever needed.

- Advantage #4. Compressed air firearms are less prone to jamming. Jamming as a result of screwed-up casing ejections are a big cause of weapon malfunction for conventional firearms. Firearms that are semi-automatic, gas-actuated, and fire bullets driven by smokeless powder are now standard fare, and these mechanical mechanisms that are powered by gas pressure from burning smokeless powder offer plenty of opportunities for jams and malfunctions. However, compressed- air-powered guns completely sidestep any problems with shell casing ejections because there are no bullet casings to eject. - Advantage #5. Compressed air firearms make less noise than black powder or smokeless-powder-propelled guns when fired. An added bonus that comes with operating at lower barrel pressure is producing less noise. The big gassy burps that come out of larger compressed-air-operated firearms are actually quite boisterous and far from quiet, yet these big hick-ups from big air rifles still produce notably less noise than the rantings of their combustion-powered counterparts. Even very large and extremely powerful compressed air rifles can be muffled to the decibel level of a sneeze if they are outfitted with good suppressors — the point is, even the big-uglies of the compressed air gun world can be made shockingly quiet.

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The image above is a screen capture from a YouTube video posted by the channel called Up North Airgunner. The screen-capture featured above is from the video titled "DonnyFL Emperor Air Gun Suppressor for the AirForce Texan Big Bore: Quieter Than Raindrops?" A screen capture from this video is included to provide a sense of how a suppressed big-bore air rifle appears. The air rifle featured in this video makes about as much noise as a sneeze.

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Many of you have probably already seen this image, but hey, even artillery can be fitted with suppressors. Image courtesy of snopes.com - Advantage #6. Compressed air-powered-guns themselves typically weigh less than their power-driven counterparts, regardless of the grain-weight of the ammo getting tossed. Compressed air guns may be kind of bulky because they typically have tanks of air attached to them; none the less, most air guns themselves can be made from much lighter materials than their powder-driven counterparts. Some of the lighter materials that can be used to make compressed air guns include aluminum, hard plastics, and carbon fiber, and using lighter materials results in lighter guns. Entire firearms made from nothing except aluminum have been produced, and they work quite well. All-aluminum firearms generally last as long as steel-parted rifles, but all of these totally aluminum guns that have been produced so far have been custom- made to be sporting equipment used by target shooting enthusiasts. So far, every one of the all-aluminum rifles that have been produced and used by target shooters fire .22- caliber match-grade conventional smokeless ammunition that produces barrel pressures of around 24,000 psi6, and air rifles typically operate at 4500-psi, so it is quite possible to make good air rifles by using nothing but aluminum. The point to remember here is that building good smokeless-powder-burning firearms by using nothing but aluminum is very possible, and recent advances in 3D-printing and plastics technology have also opened the door for manufacturing light-weight firearms

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out of all sorts of light-weight polymer components. Additionally, if steel is chosen as the material for building a big-bore air rifle's barrel, then the steel tubing and other components chosen to form this air gun can be much thinner and lighter than they would be in a powder-driven rifle, and all of the steel components in an air rifle can be made much lighter and thinner because the internal pressures in air rifles are so much lower. Examples of air gun barrels being made from nothing but aluminum can be noted by examining an air rifle made by Modoc Air Ordinance. Besides just the barrels, many other parts of air rifles, like receivers and triggers, can be manufactured by using materials other than steel. The possibility of making many parts of air guns besides the barrels out of light materials other than steel alloys is so attractive because the shock and vibrations produced by firing air guns are also much lower on account of the gas pressure used to drive the bullets being so much lower.

The image above shows an all-aluminum and custom-made target-shooting rifle. Image courtesy of wkikmedia.com

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The image above shows a custom-built all aluminum match-shooting rifle in use at a firing range. Image courtesy of bulletin.accuarteshooter.com As for the issue of how much air tanks weigh, newer carbon fiber cylinders are quite strong and actually weigh surprisingly little for the volume they occupy, so the weight of air cylinders themselves is not a big issue. On the other side of the equation, steel air tanks may be heavier, but are very cheap to produce, surprisingly shock-resistant, and they are quite durable. Aside from being just being cheap and durable, steel air tanks effectively resist taking damage from exposure to oxygen in the atmosphere, solvents, salts, and other corrosive chemicals. So, making the air tanks for compressed-air firearms from steel is the way to go? Well, no. Making the compressed air storage tanks for any air gun from any type of metal is a bad idea because metal tanks can get hot enough to burn a person's skin if they are left out in the hot sun or if they are left too close to a cooking fire. Metal air tanks could also become very cold in low temperatures and cause damage to a person's skin if they touch them without gloves or another layer of protection. A very cold air tank actually poses danger to a person's skin in the same way that touching a metal light post with your tongue in very cold weather can lead to your tongue getting stuck to the metal. In short, touching very cold metal with unprotected skin can easily lead to receiving tissue damage from frostbite. Metal tanks can also conduct electricity; admittedly, getting an electric shock through an air gun's pressure tank is not likely to be a very common occurrence, but it is worth mentioning. One solution to the problems associated with the conductivity of heat, cold, and electricity in metal air tanks is to keep them covered with layers of some type of cloth, as was done with the air tanks on Girandoni rifles back in the day, but cloth layers can easily get very dirty, worn, and unsanitary over time, so it is best to just use easily

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cleaned, and non-metallic carbon fiber tanks. Metal air tanks are also a bit heavy, so it is always best to use carbon fiber tanks to save weight because every extra pound starts to count when a gun is carried for a long time. True, if a carbon fiber air tank under high pressure were to rupture, then this situation could pose some dangers to the air gun's user, but metal tanks pose additional dangers that will be discussed later. - Advantage #7. Compressed-air-powered firearms are much less likely to overheat than their powder-powered peers. Overheating is generally not an issue for powder-burning sniper rifles, assault rifles, and pistols, but overheating can be an issue for larger machine guns that fire conventional smokeless-powder-driven bullets. Although no large fully automatic compressed-air- driven machine guns are currently on-offer to the public, several small, yet fully automatic compressed air firearms are presently sold on the civilian market. Based on current offerings, producing effective compressed-air-driven machine guns could easily be done because making large and effective air-powered machine guns would simply be a matter of scaling-up many of the currently available compressed air weapons that are small and fully automatic. So, despite the advantages offered by conventional powder-burning guns, compressed- air-powered guns will always offer the advantage of producing less heat because there is no combustion happening anywhere. Additionally, compressed-air-powered guns are not likely to overhead because they are taking high-pressure air and turning it into atmospheric pressured air, so, unless there is some combustion happening, expanding gasses will always create a cooling effect. Taking gasses from a state of high pressures to a state of lower pressure creates cold, and this principle forms the basis for modern refrigeration technology, so it seems that any fast-shooting air gun that is continuously sucking-down air will not have much of an opportunity to overheat. - Advantage #8. Compressed air driven firearms do not produce any smoke clouds, nor do they release any noxious vapors after sending bullets on their merry way. Although the problem of black-powder-driven firearms producing large amounts of irritating and blinding smoke can be minimized to a tolerable level, there is still an issue with some irritating smoke getting released. Likewise, "smokeless" powder is not entirely smokeless when it is being put to work. Moreover, whether the powder being burned to move a bullet is conventional smokeless powder, or old-school black powder, there will inevitably be some noxious gasses released that will not be nice to breath. Unfortunately, some unpleasant inhalation of noxious gasses happens whenever a powder-driven weapon is discharged, and this is particularly true when a powder-burning gun is discharged in a confined and

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poorly ventilated location; however, compressed-air-powered firearms offer no such issue. - Advantage #9. Compressed air firearms produce no muzzle flashes. True, muzzle flashes that give-away a shooters position in lowlight conditions can easily be suppressed; none the less, compressed-air-driven firearms offer the advantage of never producing any muzzle flash that would need suppression in the first place. Unlike powder-based firearms, compressed air guns never produce any light flashes from their barrels because there is never any combustion taking place. - Advantage #10. Compressed air-powered firearms do not need any propellant beyond the air that surrounds everybody pretty much all of the time. Not needing any powder or propellant other than the air we breathe is a definite advantage for air guns. True, most people take the air around us that we breathe for granted — at least until it goes missing. Examples of the air we take for granted going missing are situations like being trapped in a confined space, encountering some sort of poison gas, or doing something under water. So, yes, there are situations where the air we breathe cannot be take for granted, but for most of our lives, not having access to air is really not a big concern. Given the nearly constant availability of air, owners of compressed-air guns are almost guaranteed to never have to concern themselves with the problem of running low on propellant for their guns. - Advantage #11. Compressed air firearms can be easily, quickly, and inexpensively manufactured from plastics by using 3D printers. An air rifle's comparatively low operating pressure offers designers and builders the possibility of not only producing lighter and thinner components from steel along with the possibility of producing lightweight parts from aluminum, but the low operating pressures inside air guns allows builders and designers to use lightweight plastics to build barrels, receivers, and many other crucial components. Having relatively low operating pressures inside air rifles opens the possibility of fitting these types of guns with barrels that are really just tubes of high-strength plastic with thick sidewalls that have been created by applying layers of toothpaste-like molten plastic from the heated nozzles of 3D printers. It may not be possible to make effective compressed-air driven-firearms without using at least some metal components in places like firing hammers or air-flow-valves; however, many critical components in air guns such as pressure tanks, barrels, firing chambers, receivers, and high-pressure air tubing can all certainly be made from high- strength 3D-printable polymers such as carbon-fiber-impregnated PEEK plastics.

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So far, nobody has actually done the research, but it may be possible to produce a functional 3D-printed air gun suitable for self-defense that is totally made from 3D- printed polymer parts. For example, it may be possible to substitute rubber tubing for springs, and it may be possible to make a functional firing hammer from polymer that is simply made larger to compensate for polymer's lower weight-per-volume than steel. Previously, a few experimental, yet functional, 3D-printed guns were tested that used rubber bands in place of springs and the only metal parts in each of these experimental guns were the metal firing pins that were made from nails7. As discussed earlier, building conventional smokeless-powder-driven firearms from nothing but aluminum is totally doable, and materials engineers regard newer types of fiber-impregnated plastics to be virtually complete substitutes for aluminum for any applications a designer wishes. Although there are 3D-printing machines that build parts from steel and many other metals, these metal-shaping 3D-printing machines are typically much more expensive (50,000—1M USD8) than the machines that simply print with plastics; therefore, using 3D-printing machines intended to make metal parts is not a viable option for everyone. Many people would dislike the idea of building compressed air firearms from plastic components because plastic parts are perceived to be less durable and to have a less appealing aesthetics, so it is understandable that people would prefer high-quality metal components to plastic parts whenever building with metal is possible. On the other hand, building as many parts as possible for air guns out of inexpensive 3D-printed plastics makes sense if other options are limited and people are staring down the possibility of getting disarmed then becoming the unfortunate victims of a bloody genocide.

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The image above shows an all-polymer 3D-printed pistol barrel complete with rifling. The barrel shown above is calibered for 380 ACP pistol rounds that produce barrel pressures of around 21,000-psi. The barrel shown above has lasted for more than 8 successive firings with 380 ACP rounds in testing sessions, so it is totally possible to print all-polymer gun barrels that can easily handle the paltry 4500-psi shooting pressures that are found in compressed air guns. A 3D-printed plastic gun barrel that can withstand 8 shots at 21,000-psi worth of gas pressure could easily survive countless shots at 4,500-psi without taking any damage. The 3D-printed gun barrel shown above is part of Cody Wilson's controversial design for a 3D-printed pistol called the Lulz Liberator. Photo courtesy of extremetech.com

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The image above shows a completed Lulz Liberator pistol. The Lulz Liberator 3D-printed pistol was a product of a company called Defense Distributed that was founded by Cody Wilson back in 2012. The Lulz Liberator had an all-polymer barrel that could withstand more than one shot with smokeless powder shells, so the polymer barrel of this gun design could easily handle the comparatively mild barrel pressures found in compressed-air-based firearms. Image courtesy of fobres.com

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The image above shows a Patrick 3D-printed pistol named the PM522 Washbear .22LR revolver. Patrick is the surname of an American undergraduate university student named James Patrick who was studying mechanical engineering back in 2015 when his invention first got the attention of the 3D-printing community. Patrick's pistol is made of nylon parts that were printed on an inexpensive 3D printer, and the only metal part of the gun is a nail that is used as a firing hammer. Sets of rubber bands also substitute for springs in this pistol design. The pistol seen above is designed to fire .22-Long rounds filled with conventional smokeless powder, so this pistol can accommodate over 20,000-psi worth of barrel pressure without breaking. Patrick's design was an attention-getter because the only metal part was the firing pin, and the firing pin on this gun is a simple roofing nail; lets also keep in mind that James' pistol was also a head-turner because it was not limited to firing a handful of shots before it broke, unlike the performances of previous designs for 3D-printed firearms that were made from polymers. Patrick's 3D-pinted plastic firearm is mentioned here because the existence of this weapon proves that building very effective firearms that are powered by compressed air can be done by using 3D-printers that apply layers of common and inexpensive polymers. Image courtesy of slashgear.com, text information references courtesy of 3dprint.com

Problems with Compressed-Air-Driven Firearms ★ Problem #1. At this time, no compressed air guns that shoot bullets larger than .22 caliber are able to achieve the speeds needed to create hydrostatic shock. Yes, a few YouTube videos feature experimental air rifles shooting small bullets at more than 2,000 feet-per-second9, but any larger bullets thrown by air guns will not

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be able to achieve the speeds needed to create hydrostatic shock—at least for the foreseeable future. For those who are not familiar with the concept, the term "hydrostatic shock" refers to the shock waves that are created when a bullet moving faster than 2,000 feet-per- second strikes a living animal. Creating hydrostatic shock is a desired outcome when hunting animals because the shock waves generated from really high-speed impacts damage every organ near the spot where a bullet strikes, and these strikes from fast moving projectiles can cause almost instant death. Inducing hydrostatic shock is also desirable for military purposes because it ensures that an enemy solider that is struck by a hydrostatic-inducing bullet will not be coming back to work real-soon if he is hit anywhere in the torso. Solution to Problem #1 Add barbed and serrated internal pieces of hard metal to hollow-point air gun bullets. Ok, let's just face the facts, bullets shot from compressed air rifles will not achieve velocities of 2,000 feet-per-second or more; however, large and heavy hollow-point bullets with serrated internal spikes will do a lot of damage to any man, beast, or beast- man they greet. Consider this, getting hit with a 650-grain bullet that delvers 800 foot- pounds of energy is going to give old slow-witted Johnny quite a little ouchy, and Johnny just might have to have his mom write a sick not and send it to the principal because he will not be riding the short bus back to school for a while. So, let's face it, even if an air gun bullet cannot produce any hydrostatic shock, getting hit with a 20mm hollow-point bullet that has a barbed steel spike in the middle and produces 2800 foot-pounds is not going to be fun — no sir.

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The image above shows large-caliber hollow-point ammunition for big-bore air rifles that has steel internal pieces which are intended to pierce their target while the rest of the bullet flattens-out and delivers a huge amount of raw kinetic energy. Image courtesy of corbins.com

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The image above shows large .457-caliber 385-grain hollow point ammunition that is designed for killing big, nasty, and dangerous game. The ammunition shown above has hardened brass centerpieces designed to penetrate even the thickest skin and heaviest bone, so even if an air gun cannot achieve muzzle speeds capable to inducing hydrostatic shock, bullets like the ones seen above are still going to be effective. Image courtesy of mrhollowpoint.com

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★ Problem #2. Compressed air guns typically offer a very limited shot count. Big-bore air rifles typically use a lot of air per shot, so a typical air tank attached to a large compressed-air-driven rifle will only offer the shooter between 3—8 shots. Semi- automatic air guns are sold on the market; however, being forced to sacrifice some compressed air to reload their bullets gives these semi-automatic air-actuated firearms limited power and limited shot counts.

Having a limited shot count is a bit of a problem, particularly for this gentleman from Romania. Image courtesy of Hollywood.com Solutions to Problem #2. Hose lives matter! The first thing to mention when discussing solutions to the issue of low shot counts for compressed air guns is to consider supplying these weapons with air from hose hook-ups. Hoses are great tools for increasing the shot counts of compressed air driven firearms because they offer a cheap and easy way to connect air guns to larger air tanks, compressors, and sets of smaller tanks; all of which can keep the ravers gyrating for quite a while at your next disco party.

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Hoses are great tools for supplying compressed air guns because they are cheap and they do not weigh very much; but most importantly, lengths of hose offer air gun designers the possibility of permitting a flow of compressed air to turn corners without losing much energy. Hoses are able to guide air currents in different directions with minimal energy loss because they do not force moving air to make any sharp turns. Hoses maintain their efficiency for the same reason that fast-moving cars can make very gradual turns at high speeds without needing to slow down; however, drivers who are controlling any and all types of cars have to slow down considerably if they want to make any sharp 90- degree turns. By contrast to using air hoses, fixed air piping arrangements will greatly restrict the flow of air if there are any turns in the system that are not very gradual. Given the nice capabilities offered by high-pressure hoses, it is no surprise that many of the bigger compressed air driven rifles presently on the market work by drawing air from a cylinder that is attached to the gun, but these same firearms are also able to work by drawing compressed air by way of a remote hose connection. One fix for the problem of having to live with low shot-counts in smaller compressed- air-powered firearms is to have multiple 500cc tanks of air available that are attached to the guns themselves and mounted under the barrels of these guns. Besides just attaching multiple supply tanks under the barrels of air guns, additional air cylinders can be placed on the sides of gun barrels as well. Attaching the air cylinders that power a rifle under the barrel of that gun, and perhaps attaching additional air tanks on the sides of the barrel as well would be a good design practice because in this type of layout the air tanks are not placed too close to a shooter's body. Equipping the 500cc air tanks needed to power compressed-air firearms with quick- release fittings is also a good practice because it facilitates rapid air tank replacement in a pinch. Despite all of their shortcomings, the AEA Airgun company from China has developed a decent set of 500cc compressed air cylinders that hold 4500-psi worth of air and can be simply twisted on and twisted off with one quick flip of a wrist. In order to be useful, large fully-automatic air guns of any useful size need to be hooked- up to air hoses that can continuously supply volumes of air that are sufficient for continual operation, but if a sufficient and continuous supply of high-pressure air is available, then shooters can have themselves quite a ball and a biscuit firing these heavy, air-powered, machine-guns.

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The photo posted above shows an Airforce Texan big-bore air rifle firing from a connector hose that is attached to a large cylinder of highly compressed air. Image courtesy of pyramidair.com

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The image shown above is a 50-Caliber Piledriver rifle made by the Hatsan air rifle company. Notice how at least one more air tank like the one already attached to the rifle could easily be fitted underneath the barrel in the front portion of the gun. It seems that two more tanks like the one already attached to the rifle could easily be fitted under the barrel if weapons designers do not mind having a bit of air tank jutting out past the tip of the barrel. Each additional air tank like the one pictured could be fitted under the barrel in order to gain a larger shot count. A set of high-pressure air tanks could be made from light-weight carbon fiber and connected to the firing valve by lengths of flexible air hose, and the fittings of each hose could easily be equipped with emergency low-pressure shut-off valves. Each of the brackets holding an air tank could also be equipped with quick-disconnect tank fittings like those developed by AEA Airguns in order to facilitate fast reloading. Image courtesy of airgunwire.com

The rifle pictured in the illustration above has a spherical air tank mounted under the barrel in a perpendicular arrangement that places the tank's outlet at a 90-degree angle to the barrel of the weapon. This illustration is included to show that several spherical carbon-fiber air tanks can be mounted in a row under the barrel of a tactical air rifle and connected to the firing valve with high-pressure air hoses. Spherical air tanks offer the advantage of being stronger and harder to rupture than oblong cylinders; however, spherical air tanks do not lend themselves to efficient packing and storage in the same way as oblong air cylinders. Image courtesy of heritagearmssa.com

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The photo posted above shows how multiple smaller air tanks could be placed along the sides and bottom of a tactical air rifle and then connected to the firing valve with sections of high-pressure air hose. Image courtesy of utahairguns.com

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The image above is a screen capture from a video, and the image above shows a quick-connect air hose designed to hold air compressed to 4500-psi. The equipment seen in the photo above caters to the paintball gun industry, and the paintball gun industry may be a bit different business than the big-bore air gun market; none the less, this industry is a nice potential source for many cheap components that are designed to work with air pressured to 4500-psi which could be incorporated into big-bore air rifles. Image courtesy of ANSgear.com Although they do not exist at this time, medium-ranged tactical air rifles designed to fulfill the role of assault rifles could draw their mojo from several air tanks mounted under their barrels. Tactical air rifles that draw their power from multiple sources could take air from not only tanks mounted under their barrel on their front ends, but they could also draw air from tanks mounted on the sides of their barrels. Tactical air rifles could additionally get their courage from air hoses connected to light-weight and armor- plated carbon fiber backpack units filled with many small air bottles that are connected together by high-pressure hoses. Tactical air rifles could also be supplied by a combination of tanks mounted on the rifles themselves that would work in conjunction with modest-sized backpack units filled with many small carbon-fiber cylinders. Building with redundancy is a good idea when designing proper air guns that are suitable for self-defense applications because having many sources of air ensures that these weapons will not easily fail, nor run out of air quickly.

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Admittedly, the paintball gun shown above is a bit over-the-top and gonzo, but this photo is useful because it shows how a tactical air rifle could draw its power from many small cylinders hooked-together by high pressure air hoses. Although the paintball gun industry is a bit different than the big-bore air rifle industry, there are some components and technologies that can be applied in both types of products. Image courtesy of mcarterbrown.com ★ Problem #3. Structural failures and large leaks in high-pressure air cylinders pose danger. Yes, having a cylinder containing air compressed to 4500-psi that is kept near to a person's body is like having a hand grenade pressed to their body. Sure, keeping a cylinder pressured up to 4,500-psi near to your body is like keeping a hand grenade that could potentially explode and inflict grievous bodily harm a little too close to the body for comfort. Indeed, having a cylinder filled with very pressured air that is held very near to a person's chest or arms certainly poses some type of endless potential danger. Solutions to problem #3. The first issue to address is the question of how likely the tanks that are mounted on air guns are to rupture in the first place. The truth is, tales of tank breaches are almost unknown for modern air guns, and this information comes from Pyramid Air, which is one of the biggest international retailers of air guns that incorporate high-pressure tanks. True, there were recorded incidents where the old Girandoni air rifles suffered from tank ruptures that caused injuries, and even deaths; that having been said, the air cylinders used on modern air guns are typically able to withstand about three times the pressure of their official ratings, so petty issues like leaving an air gun too close to a camp fire, or accidentally leaving an air rifle out in the sun on a hot day are not likely to result in any air tanks exploding. The only recent example of an air rifle having a dangerous breech was noted because the idiot whose air rifle exploded on him was filling his tanks past capacity and using

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pure oxygen from a welding tank as the filling gas10. Incidentally, the oxygen-tank-filling moron from this tale of woe was not actually injured when his air rifle tank exploded; doofus was just startled. OK, let it be established that air tank breaches are not really a problem for the air gun sporting market; right, but the issue of dangerous tank breaches still has to be acknowledged if air-powered-firearms are to be used for self-defense purposes. The first solution to the problem of having a lot of stored energy lurking within air bottles is to diversify the holdings. So, what is meant by the term "diversify the holdings"? In this case, diversifying the holdings means that the compressed air that powers these guns is stored in bottles no larger than 500cc. However, anti-material compressed air rifles may be an exception to the rule mentioned previously because they are so big, plus these types of shooting appliances are not carried around by a single person, unlike with other types of compressed air guns. The idea behind storing firing air in multiple small bottles is the principle that if one smaller air tank ruptures, then having an individual small tank break will limit the amount of damage possible. Basically, for safety purposes, the compressed air needed for a swinging party at the bachelor pad can be stored in more than one small tank on an individual gun. So, for safety sake, each of an air gun's small storage tanks could be connected to a set of high-pressure hoses, as opposed storing all of the powering air in a single large tank that would make a huge explosion if it were ever to get breached. Air guns could also get their fix of compressed air by way of armor-plated carbon fiber backpacks filled with many small compressed air cylinders. These light-weight, yet sturdy, carbon-fiber backpack supply units could also be designed to channel high- pressure air out to designated outlet channels within the backpack's casing in the event of a cylinder breach, and this set of high-pressure air emergency outlet channels would exist in order to keep the wearer safe if a tank should ever spring a really big leak. Likewise, a set of air cylinders mounted under the barrel of a tactical air rifle could be encased in a light-weight carbon-fiber shell that would channel any high-pressure air from a cylinder breach out to designated safety outlets in the event of a tank rupture. High-volume leaks in any high-pressure air hoses or piping could also easily be shut- down almost instantly by vales designed to work by spring pressure, or by rubber bladders filled with compressed nitrogen. Several designs exist for valves that close when unsafe levels of low-pressure develop, and these low-pressure cut-out devices are also cheap and easy to manufacture. Several low-pressure cut-out valves could also be set in redundant patterns that would close any high-pressure air hoses or piping whenever pressure levels drop below a certain level.

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The image above shows a low-pressure cut-off valve. Spring-loaded low-pressure cut-off valves are cheap, plus they could easily be installed in many different locations within an air gun's supply system. A network of low-pressure shut-off valves could be added to multi-tank air gun designs in order to function as a preventative measure against dangerous high-pressure air leaks. Low-pressure cut-off valves, like the one shown above, are simple devices that use a diaphragm and a spring to regulate pressure. Spring-loaded low-pressure cut-out valves like the one seen above will close if the pressure in the pipe or hose drops too low. An example of an unsafe drop in pressure would be something like having compressed air is rush out of a broken hose, and a valve like the one seen above would close automatically in a situation like this because the internal spring-loaded diaphragm would push down and seal the line when the pressure dropped too much. Devices like the one above are installed to halt leeks on water lines, gas lines, and conduits carrying all sorts of substances. Image courtesy of BES.co.uk Another safety precaution worth incorporating into defense-grade air-driven weapons would be to avoid using any metal in the main bodies of the air tanks. Metal parts could be incorporated into air tanks in a safe manner, provided that the metal pieces are only

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used for things like the valves and connectors for tanks, but it is best to never use any metals to make the bodies of the air tanks themselves. Metal should always be avoided as a construction material for air rifle tanks because metal cylinders that are made from steel, aluminum, or titanium create fragmentation and jagged edges if they rupture, so using carbon fiber to make air tanks for defense-capable air guns is the way to go. In previous centuries, fashioning pressure vessels for air rifles from copper was a popular practice because copper was relatively easy to work with; however, copper air tanks became the way of choice because they offered the advantage of not producing jagged edges or shrapnel if they were to explode. So, it seems that making air tanks from copper or brass might be a solution to issues concerning the safety of high- pressure air vessels; on the other hand, both copper and brass are relatively expensive and heavy, plus both of these materials have all of the problems with temperature and electrical conductivity that are endemic to metals in general. True, making pressure vessels from copper or brass will work for constructing high- pressure air guns because copper-based alloys are strong enough to hold the needed pressure, and they are easy to form and fashion into the desired shapes, plus using copper-based alloys like brass makes for safer air tanks. None the less, due to their weight, and all of the other problems associated with using metal cylinders, air tanks made from copper or copper-based alloys should be viewed as a practice to avoid if other choices are available.

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The image posted above shows an old English compressed air rifle that has a braised copper pressure vessel with a threaded connector that lends itself to being easily replaced. Making pressure vessels from copper was a popular practice for old-time air rifle craftsmen because copper is a softer metal that is relatively easy to shape; moreover, air tanks made from copper will not produce shrapnel or jagged edges if they explode. Image courtesy of beemans.com Lastly, for high-pressure air tanks mounted on big-bore air rifles that are designed to be used as sniper rifles, placing an air tank made from any workable material, including steel, in the stock of the rifle may not really be much of a problem because the people using these slug-throwers out in the field are generally not participating in close- quarters shooting matches where tank breaches are most likely to happen. ★ Problem #4. You need a suitable pump to charge an air gun. Yep, some type of suitable high-pressure pump will be necessary to fill an air gun's power supply; and regrettably, just puffing on a straw will not provide the pressure needed to move bullets at the kinds of speeds we are seeking. So, how does one go about ensuring that there will always a means to fill their little Easter basket with candy? Solutions to Problem #4. Electric pumps powered by AC and DC currents that are capable of achieving the pressures needed to operate modern air rifles are cheap, quiet, fast, and compact. Small air pumps that can operate out in the field can also be powered by tiny piston engines that could run on all sorts of fuels such as gasoline, propane, vegetable oil, and ether. In addition to using electrical pumps or piston-engine-driven pumps to fill air gun tanks, muscle-powered manually driven pumps that can recharge depleted air cylinders out in the field are also very effective, cheap, and easy to get.

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The image above shows a Nomad II portable air gun compressor unit. The Nomad unit shown above is capable of producing 4500-psi, and this unit runs off of standard wall-socket current plus 12-volt DC electrical sources found on boats, other types of vehicles, and stand-alone car batteries. Image courtesy of mountiansportairguns.com Many manufacturers now produce very inexpensive 3-stage hand pumps that are capable of creating pressures up to 3650 psi. One manufacturer of hand-operated pumps now offers inexpensive 4-stage pumps that are easily capable of reaching 4500 psi. 3 and 4-stage high pressure air pumps look like traditional bicycle pumps, except they are a bit wider in their bodies. Multi-stage air pumps achieve their high pressures by having pump plungers of different sizes compress the gas. In a multi-stage manually powered pump, the first stage has a large plunger head that creates lower air pressures, the second stage has a smaller plunger head than the first stage which creates higher air pressures than the initial pump chamber, and the 3rd and 4th stages have plunger heads that are very small so that they can achieve super-fly air pressure.

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The image above is a screen capture from a listing for a high-pressure manual air pump on ebay.com Notice that the pump pictured above does not cost very much, nor is it very heavy or bulky. Air rifles from the 1500s—1800s only used single stage pumps that were capable of pressuring an air tank to around 800 psi, and operating pressures as low as 500 psi were also used to power big-bore hunting rifles. The big-bore hunting rifles of those days often used rotating cams as opposed to springs and hammers to open their firing valves after their triggers were pulled. The old low-pressure big-bore antique air rifles from previous centuries could achieve around 300 foot-pounds of energy by shooting 200— 400-grain lead balls that were pushed out of the rifles by air compressed to around 500—800-psi. So, yes, it is actually possible to make large air rifles that operate on surprisingly low pressure. The point behind mentioning the pressures inside of old air rifles is to emphasize the fact that air guns can be powered-up to useful levels even with air pumps that are home-made, powered by a person's arms, and rather basic — welcome to the ghetto. In contrast to newer air rifles, the very old types of compressed air rifles got their power by keeping their firing valves open for as long as possible, and by having long barrels, so this method of shooting by using low air pressure that pushes a piece of lead down a

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long runway does works, but it offers limited power compared to the high- pressure "hard air" types of modern air guns. The best power offered by old-style low- pressure big-bore air rifles is around 400 foot-pounds. Thing is, 400 foot-pounds is enough muzzle energy to kill a large boar. The take-away from a discussion about low-pressure big-bore air rifles is to remember that if times become desperate, and even black powder is hard to acquire, then air guns can be still be made and used for hunting and rudimentary self-defense. Functional large-bore air rifles can be made with basic tools, even when nothing else is available, and crude hand-operated single-stage air pumps that are made from whatever materials are available can be also be used to charge hand-made braised copper pressure tanks. So, remember sports fans, it is possible to make rudimentary, low-pressure, home-made air rifles when other options for community and individual self-defense are limited11.

The image above features a Japanese Kunitomo air rifle. The image of a Kunitomo is included to provide a visual example of a low-pressure big bore air rifle that has a firing mechanism that is actuated by a rotating cam as opposed to a striking hammer. Image courtesy of blog.livedoor.jp

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The image seen above depicts a Japanese Kunitomo air rifle from the 1820s. An image of the Kunitomo air rifles from Japan is posted to provide an example of a low-pressure air rifle that uses a cam to actuate the release of air from the storage tank, as opposed to using a spring and hammer like most modern high-pressure air rifles. Image courtesy of blog.livedoor.jp

The illustration shown above provides a little bit of basic insight into the workings of a low-pressure firing system for big-bore air rifles. Notice how the firing action shown above uses a rotating cam as opposed to a striking hammer to open the firing valve. Image courtesy of heritagearms.com

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The illustration featured above provides a slightly different schematic showing a little different type of cam-action firing mechanism for a low-pressure big-bore air rifle. Image courtesy of hertigearms.com

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The illustration on the previous page provides a visual reference for how a cam-action air rifle's firing mechanism operates. Illustration courtesy of forum.haszysz.com ★ Problem #5. Even if you have a suitable manual air pump, it still takes a bit of time to fill an air tank, plus it takes a bit of sweat and toil to manually charge an air gun. This is true, it will take a bit of straining to manually recharge an air cylinder out in the field. Solutions to Problem #5. Taking an air cylinder from the starting point of atmospheric pressure and then manually raising that cylinder's pressure to 4500-psi will require hundreds of pump strokes and quite bit of time; however, once an air cylinder has achieved its needed operational air pressure, then every pull of the trigger will typically require around 3—4 strokes from a compatible manual air-rifle-filling pump to replace what has been lost. So, for example, taking three shots with an air-powered sniper rifle will amount to around 12 complete strokes of a manual air pump, which is not really going to take much time nor demand a huge amount of physical work. The filling time needed for tactical air rifles may be a bit longer, and it might demand more work, but that is to be expected if a tactical air rifle is powered by as many as 12 500cc compressed-air cylinders that need to be recharged. If a tactical air rifle were to fire 50 times at a nice neighborhood ice-cream social, then that would translate to around 150—200 refilling pump strokes. Completing 150—200 strokes from a manual air gun pump would probably demand about 10—20 minutes of work, but this work-load could easily be divided among more than one person. ★ Problem #6. Air guns lose pressure with each successive shot fired. Yes, unregulated air guns do lose power with each successive shot. The phenomenon where an air gun loses power with each successive shot is called "The Korean Cliff" by those who know a thing or two about air guns. The Korean cliff is seen most-readily when looking at graphs showing bullet velocity and foot-pounds over a spread of several shots. The term "Korean Cliff" originated from imported Korean-made big bore air rifles losing huge amounts of power between the first and second shots; hence the term "Korean Cliff." Solutions to Problem #6. One solution to the Korean Cliff problem is to build pressure-regulated air guns, but having pressure-regulating parts in an air gun adds to the cost of that individual firearm, and having a pressure regulator inside an air rifle also adds to the number of things that can malfunction. So, when designing compressed air firearms with self-

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defense applications in mind, it is imperative that the guns have as few parts as possible in order to be as reliable as possible, and to be as easy to troubleshoot and repair as possible. In summary, having an air regulator inside an air rifle is not the best way to roll because regulators create troubling reliability issues and raise the production cost, and they also decrease the available power. An example of how a regulator works would be to think of an air rifle that has a supply tank that holds 4500-psi; however, having a regulator installed decreases the air pressure used to move the bullets down to a less muscular 3,000-psi per shot, so there will be less power per available for every bullet fired. On the up side, having a regulator within a compressed-air-powered firearm also means that all of the shots made with those types of guns will have the same power, so there will be no issue with Korean cliff types of power curves. Regulated air guns also provide the advantage of offering a few more shots per tank, but of course, at a decreased power rating. Despite the advantages offered by regulators, the most cost-effective and simple solution to the Korean cliff problem is to simply have no regulator at all in an air gun and to use a conventional hammer and spring firing mechanism, except with the pressure on the firing spring set a bit low so that the first few shots are less powerful than they could be; but on the flip side, some air would be saved in the early shots in order to add a bit of pepper to later shots. So, essentially, setting the firing springs with a bit less tension will even-out the power curve for compressed air firearms, and this process of deliberately down-tuning the firing spring makes having regulators unnecessary. When considering how a spring-tuning regulation process for an air gun works, another factor to consider is the opening time for a firing valve as it relates to each stroke of the firing hammer. For example, the first strike of a firing hammer is always going to open a firing valve for a shorter time, and an initial stroke from a firing hammer will not open the firing valve as wide as it would on later shots because the air pressure on the other side will be highest during the first few shots. So, the early strikes from a firing hammer open a firing vale for a shorter time and do not open the valve as wide; however, later strikes from a firing hammer that exert the same amount of force will open the firing valve for a longer time and open the valve wider because later hammer strikes are working against air with less pressure. Any air gun without a regulator will still suffer from the Korean cliff problem to some degree, make no mistake about that; however, having a well-tuned hammer and spring working in tandem tends to naturally even-out the drops in power that inevitably happen over a series of successive shots12.

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The image above is admittedly a bit grainy, but it does provide a basic sense of how many air rifle designs function. Note: The air rifle pictured above does not have a regulator. Image courtesy of daystate.com

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The image posted above shows the basic layout of an Air Force Texan firing valve. Notice how the Texan's firing valve is very simple and efficient. Note: The Texan valve seen in the illustration above does not have a regulator. The "Top Hat" piece is where the ring-shaped firing hammer strikes and releases the firing air. Image courtesy of stealthresource.org

The image above shows the front part of the firing mechanism for Air Force Texan rifle. The diagram above includes the forward-mounted firing hammer and spring arrangement in a Texan big-bore air rifle. Image courtesy of stealthresource.org

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The image above is included to show an external view of the "Top Hat" part where the firing air enters the bullet chamber on a Texan big-bore air rifle, and this photo is also included to show an external view of the donut-shaped hammer and the spring that compresses the top hat and sends a blast of high-pressure air into the rifle's barrel. Image courtesy of airgundepot.com

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The valve seen above is an aftermarket high-flow valve for the Airforce Texan Talon air gun models. Just for reference, no pressure regular is present, and this valve is ready to be installed in a Texan Talon series air rifle. The photo above is included to illustrate the simplicity of a Texan's firing valve. Image courtesy of aliexpress.com ★ Problem #7. Compressed air power does not lend itself well to powering sidearms. Compressed air pistols have been around as long as compressed air firearms have been in use; but still, compressed air is not a great choice for powering sidearms. The first reason that compressed air is a poor choice for propelling pistol rounds is because making an air-powered pistol that can generate at least 300 foot-pounds of muzzle energy requires designers to use a barrel that is at least 18-inches long. The comparatively low gas pressures used to drive bullets out of air guns require longer barrels to achieve any semblance of decent projectile speed because longer pushing times are needed to achieve decent muzzle velocities with such low pressures.

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So, short rifles, otherwise known as carbines, can easily be powered by compressed air; none the less, the barrel lengths needed to make effective pistols that use compressed air as propellants creates a problem. The second reason that using compressed air to power a pistol is not very workable is because powering a pistol that is suitable for real self-defense applications requires using a bullet that is at least 50-cailber or larger. Unfortunately, it seems that achieving respectable ballistics numbers for an air pistol actually requires using bullets that are 72- caliber or larger. The third reason that compressed air does not lend itself well to powering pistols is because some type of bulky air tank is needed to power a compressed air pistol. Concerning the space that air tanks require, true, many of the antique air pistols that sit in museums and private collections have rather small air tanks attached to them, but they are typically only good for one shot, or they may hold more than one shot, but they produce levels of power that are way too low to act as good tools for promoting simpatico. So, although carbon fiber air tanks do not weigh much, they do occupy a lot of space, and having to include light, yet bulky, air tanks into the design of an air- powered pistol will result in a final product that is it a bit too large and cumbersome to work as a sidearm.

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The image seen above is a 20mm(82-Caliber) bolt-action pistol that is used for hunting. A large and bulky design like the one seen above is necessary if an air pistol is to offer any semblance of the kind of muzzle energy a pistol needs if it is going to serve as a proper tool of understanding. Image courtesy of mrhollowpoint.com

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The image seen above is a screen capture from a YouTube video posted on the American Airgunner channel from May 30, 2019. The pistol seen above is called the Scarab, and it is basically a shortened version of the Zeus model of 72-caliber air rifle that is manufactured by the AEA Airgun company. The "pistol" seen above produces 600 Joules, or 461 foot-pounds, of muzzle energy. This image is presented to illustrate the design parameters needed to achieve any sort of respectable ballistics numbers for an air-powered pistol. Solutions to Problem #7. Sorry, there really are no effective ways to compensate for all the problems encountered when trying to design a pistol suitable for self-defense that is powered by compressed air. No matter what, an air pistol will need a long barrel to achieve any sort of decent muzzle energy, so it will not work well as a sidearm, and regardless of whatever arrangement a designer chooses for positioning the air tanks on a pistol, the air tanks will inevitably wind-up occupying so much space that the convenience associated with packing a sidearm will be lost. ★ Problem #8. Compressed air is ineffective as a propellant for shotguns. A blast of compressed air that has been unleashed from a storage tank by tapping a firing hammer onto a spring-loaded valve simply does produce enough muzzle pressure to get small loose bits of material moving with enough speed to work as a functional shotgun. Using compressed air to move solid single slugs of material with enough speed to produce workable firearms is already done, so the concept of using compressed air to move a solid slug is proven; however, compressed air can only

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move a bullet with enough speed to function as a decent firearm if there is a long enough barrel, a tight enough seal around the single bullet, and sufficient air pressure to drive this single bullet. Yes, a few companies currently produce compressed-air-powered shotguns, but the results have not been very impressive. The few compressed-air-powered shotguns that are produced and offered on the market work by encasing buckshot into large single bullets that have thin plastic outer shells that are designed to open after they leave the gun's barrel. Encasing backshot into large bullets that are designed to open once they have left the nest may work as a means of powering a compressed air shotgun, but the velocity of the buckshot that leaves an air-powered shotgun is just too low to offer enough range or power to kill anything other than small birds or rodents that are within about 10—15 feet of the shooter. A typical shotgun drives pellets at around 1100 feet per second, and so far, nobody has been able to develop a compressed-air-powered shotgun that moves buckshot faster than 750 feet-per-second. As listed on the website closefocusresearch.com, pretty much every conventional smokeless-powder-gulping shotgun that is currently available, regardless of its caliber, moves its wares with barrel pressures between 11,500 and 12,500-psi; needless to say, those sort of pressure numbers are not going to be available for air-driven shotguns any time soon. Solutions for Problem #8. So far, nobody has really developed a way of making compressed air viable as a driving mechanism for shotgun pellets.

The Current State of Compressed Air Firearms Sniper Rifles: There are currently no air rifles on the market that are dedicated tools of self-defense; however, there are quite a few well-developed air-powered hunting rifles that are currently for sale to the general public. Many effective sniper rifles started out as hunting rifles, so the current crop of high-powered big-bore air rifles sold as sporting equipment are in fact quite suitable for conversion to sniper rifles13.

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The image above shows a very dead cape buffalo in South Africa. This big, hairy, snort'n bovine received a free pass to big-old snort'n buffalo heaven courtesy of an air gun. This image is included to show that air rifles can pack a lot of power. Image courtesy of africanairhunting.com

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The image above shows a rather large elk that was bagged with one shot; courtesy of a big-bore air rifle. This photo was included to illustrate the power, range, and accuracy of air rifles. Image courtesy of extremebigboreairrifles.com Only some of the big bore air rifles that are currently on sale to the general public offer the qualities needed for a proper sniper rifle; none the less, a few air rifle manufacturers offer products that would make great sniper rifles. Some big-bore air rifles would make great sniper rifles not just because they can hit things at long ranges with a lot of power and accuracy, but also because they are lighter and more quiet than conventional sniper rifles. Compressed air rifles additionally offer the bonus of requiring a lot less cleaning. True, compressed air sniper rifles may need to be refilled after a few shots are taken, but these rifles can be hooked up to air hoses, and luckily, the refilling processes for 500cc air tanks are pretty fast and easy. Lastly, toting the manual air pumps needed to recharge the tanks that power compressed-air powered sniper rifles is not too much of a hardship because these manual pumps are not very large or heavy. So, yes, there are high-powered air rifles currently sold to the public that will function quite well as sniper rifles because they have the range, accuracy, and power to

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get the job done; except not every high-powered big-bore air rifle presently sold will fit the bill. In a video featured on his YouTube channel called Mr. Hollowpoint, the man who runs this channel produced a video called "Who makes the best air rifle?" where he discussed his recommendations for first time air rifle buyers. In his video directed at first time air rifle buyers, Mr. Hollowpoint says that the big bore air rifles with the most power are those that provide a straight line between the air source, the receivers where the bullets rest, and the barrels of the gun. So, basically, any of the big-bore air rifles presently sold that have a front-mounted air tank which requires the driving air to make two sharp turns before entering the gun barrel will not produce enough power to work as proper sniper rifles because forcing bullet-driving air to make any sharp turns greatly decreases the shooting power on tap. The high-powered and long-range air rifles currently on the market that would make good sniper equipment are all single-loaders where the breach has to be opened and each bullet has to be manually placed inside the firing chamber. For hunting rifles, having slow manual-loading systems works just fine, and this manual loading arrangement where each bullet has to be placing the firing chamber by hand may also be barely workable for sniper rifles; none the less, having the ability to make quick follow-up shots is still nice. During the course of an email correspondence with an air gun manufacturer, it came to light that there are currently a few aftermarket specialists who are working to create a clip-fed bolt-action aftermarket version on the 50-caliber Texan Big Bore air rifle, so creating a bolt-action version of the Airforce Texan rifle is not too difficult. It would also not be too difficult to design an air-powered sniper rifle that would have a slam-fire loading mechanism designed to permit really rapid follow-up shots. Admittedly, there are some safety concerns that arise from rear-mounted air tank designs like the Airforce Texan, and these concerns arise because the shooter is putting a cylinder of such high-pressure air so close the human body, but having stock-mounted placements for an air cylinders may not matter that much for sniper rifles. To counteract the dangers associated with stock-mounted air tanks, a set of front-mounted air tanks could connect with the back portion of the rifle by way of a flexible air hose.

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The image above shows how the operating air flows in a straight line from its source in the stock-mounted tank, through the receiver, and out to the barrel in an Airforce Texan Big Bore air rifle. The Texan's inline-oriented air flow design promotes maximum firing efficiency and maximum power, so any air rifle repurposed as a sniper rifle will probably need to have a similar straight-line airflow design. A straight-line design like the rifle seen above will generate 1200 foot-pounds of energy when fitted with a 4500-psi air tank, which provides up to 400 more foot-pounds per shot than a rifle without a straight-line design. Image courtesy of airforceairguns.com

The image above shows a close-up photograph of a .45-caliber Airforce Texan air rifle. Notice how the air source is placed directly in line with the firing valve, the bullet chamber, and the rifle's barrel. The straight trajectory of the firing air, and the well-enclosed bullet chamber provide the factors necessary to create a design that produces the most power for whatever air pressure is present. Image courtesy of utahairguns.com

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The image posted above shows a hunting rifle made by Extreme Air Rifles that comes in a variety of calibers. This image is included because many models of big-bore air rifle have a similar design where the pressure vessel is placed at a 90-degree angle to the firing chamber. The design of the rifle seen above is not as efficient at a straight-line arrangement; however, models of air rifles with a design similar to the rifle seen above will deliver more power than a design that forces the firing air to make two right-angle turns. Photo courtesy of extremearirifles.com

The image above shows the flow of air from the storage tank to the end of the barrel in a Hatsan Piledriver big-bore air rifle. Notice how the air flow for the Hatsan rifle must make two 90-degree turns before it leaves the barrel of the rifle. Having two sharp changes of direction per shot for the airflow within an air rifle results in less power, so any design where the firing air must change directions is unsuitable as a sniper rifle. The Hatsan rifle seen above will generate around 800 foot-pounds of power when shooting from a 4500-psi air tank, which is around 400 foot-pounds less than the Texan when shooting with the same air pressure and pushing the same bullet. Tactical Air Rifles: Thus far, nobody has taken the time to develop a tactical air rifle that is designed to fill the same role presently filled by assault rifles. The truth is, making tactical air rifles is certainly possible, but these rifles will be bulky, comparatively underpowered, and

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they will also suffer from a somewhat limited shot count, so using tactical rifles that burn smokeless powder or black powder would always be a better choice. Despite the inherent shortcomings associated with powering tactical rifles by compressed air, designing and building compressed-air-driven tactical rifles is still worth doing because these types of guns can be used when other types of propellants are in short supply. It is certainly possible to make semi-automatic air-powered rifles that are capable of producing around 800 foot-pounds of muzzle energy, but such weapons would require so much air to operate that they would probably need backpack-mounted supply systems to deliver any decent shot count; and even then, these semi-automatic tactical air rifles would still be likely to offer relatively low power; plus, they would still provide their users with a limited supply of party favors to send their friends. When looking to choose a loading mechanism that will conserve air and deliver the best possible shooting power while also permitting a fairly rapid rate of fire, the slam- fire pump-action method of loading offers an attractive possibility. It would also be best to design tactical air rifles with an inline flow of air similar to that of the Airforce Texan rifles in order to gain the most power for the air available; therefore, the air supply for the firing valve in a tactical air rifle could be directed from the storage tanks to the firing valve by using flexible air hoses. ` For those who are unfamiliar with the concept of "Slam-fire" loading actions, this term refers to pump-action firearms that allow the user to hold down the trigger and fire by simply actuating the pump mechanism. Shooters using slam-fire actions are able to fire so quickly because they are spared the need to pull the trigger after each bullet has been placed in the firing chamber. Actuating firearms by using a slam-fire operating mechanism is a proven concept, and not a new idea. In World War I, the American army issued slam-fire shotguns to many of their soldiers, and these pump action shotguns were called "Trench Guns." The reason slam-fire mechanisms provide such high rates of fire not only because they forgo the need to pull the trigger after each loading motion, but they also offer such fast shooting because the motion of wracking this type of loading system is very ergonomic and natural, so this type of movement can be done with the same speed as pulling a trigger. Tactical air guns could also fire very rapidly if they are fitted with slam-fire mechanisms because the loading wrack on a slam-fire air gun will not have to travel very far to load each individual bullet because there are no bullet casings. By contrast, the 3—4-inch length of conventional shotgun shells requires a longer wracking motion, so the rate of rife for slam-fire shotguns is inevitably slower than it would be for an air rifle that fires bullets that are about one inch in length. In other words, having a longer bullet

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requires a longer wracking motion for a pump-action mechanism, and bullets that have no cases lend themselves to short wracking motions of two inches or less. Another point worth mentioning in a discussion about slam-fire-actuated tactical air guns is the issue of outfitting these types of guns with balanced firing valves. Balanced firing valves work by allowing a bit of air from the high-pressure side of a firing valve to exit through the valve's firing stem, or "poppit" as it is called, in order to create a relative pressure equilibrium on both sides of the valve. A balanced firing valve that Allows a bit of high-pressure air to reside on the outside of the firing valve could be considered a high-pressure-actuated type of balancing valve. Conversely, some balanced valves work by allowing a bit of comparatively low-pressure atmospheric air to reside on the side of the high-pressure, or "strong air," and like a high-pressure-actuated balanced valve, a low-pressure-actuated type of balanced valve does not take a huge amount of force to open. So, think of it this way, a firing valve holds back high-pressure air that wants to escape, and a balanced valve lets a little bit of sequestered high-pressure air from the tank, or low-pressure atmospheric air, into a small chamber on the other side of the valve in order to create an equilibrium of pressure on the firing valve. Whichever direction the balanced valve favors, whether it be low pressure on the strong side, or strong air on the atmospheric side, the end goal is to have a firing valve that opens with less force. Many of the big bore air rifles out in the market do not have balanced valves, for example, the Airforce Texan series does not have balanced valves; however, for a slam- fire air rifle, having a balanced valve would make sense because these types of vales permit very easy setting for the firing spring. Equipping slam-fire tactical air rifles with balanced vales seems to be a good idea because a light wracking motion that does not require a lot of muscle power will facilitate faster and more accurate shooting, and a reloading motion that requires less force will cause less fatigue for a tactical rifle's user. Luckily, balanced firing valves are not too hard to produce, nor does having a balanced valve seem to greatly reduce a gun's reliability. The rifles made by American Air Arms have patented balanced firing valves, so these rifles do not require heavy spring forces to operate; therefore, it takes less than two pounds of pull to set the firing springs on these rifles. The point to remember is this, balanced valves have the potential to create feather-light cocking motions for tactical air rifles which lend themselves to fast shooting14.

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The photo above shows a design for a regulated valve where the designer intended to create the cheapest and most reliable balanced air valve possible. This design seen above is called "The Simplified Balanced Valve" The valve pictured is not designed to be installed in an "inline" air flow design like that of the Airforce Texan rifles; however, some type of high-flow balanced firing valve could easily be developed to serve slam-fire rifles with an inline air flow design. Image courtesy of gatewaytoairguns.org

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The image above provides a basic visual reference for how a standard firing valve works. For the symbols listed in the above illustration, "HPA" designates high pressure air, and "ATM" and "P" designate atmospheric pressure. Image courtesy of hardairmagazine.com

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The illustration posted above is provided to furnish a visual representation of the basic operation principles of a balanced firing valve for an air gun. The valve pictured above works by allowing a small amount of high-pressure air to exist on the low-pressure side of the valve, which in turn creates a valve that requires a lot less spring force to open. For reference, the symbols listed in the above illustration, "HPA" designates high pressure air, and "ATM" and "P" designate atmospheric pressure. Illustration courtesy of hardairmagazine.com

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The illustration above shows a balance firing valve that uses a pocket of low-pressure atmospheric air on the side of the highly compressed "strong air" to achieve a relative pressure equilibrium for both sides of the valve. For reference, the symbols listed in the above illustration, "HPA" designates high pressure air, and "ATM" and "P" designate atmospheric pressure. Illustration courtesy of hardairmagazine.com It would also make sense to place the sets of air tanks that power tactical air rifles in the forward part of each rifle below the barrel, or to mount the air tanks on the sides of the barrel in order to keep the potentially dangerous cylinders of compressed air a safe distance from the shooter's body. Other options for powering slam-fires tactical air rifles are to use redundant sets of high-pressure steel-braided air hoses that are hooked-up to armored backpack units which are filled with several small carbon-fiber air tanks. Another option is to power tactical air rifles by using a combination of several gun- mounted air tanks that work in conjunction with larger backpack-based supply units that are connected to the rifles by lengths of high-pressure hose. Ideally, a tactical pump-action air rifle would fire bullets that are 50-caliber or larger at a velocity of 900+ feet-per-second, and in a favorable scenario these types of rifles would also produce over 800 foot-pounds of muzzle energy for the first 10 shots. Additionally, a decent tactical air rifle should be able to shoot a minimum 30 rounds before needing any of its quick-release-equipped air tanks replaced. Later discharges for a tactical air rifle may have as little as 400 foot-pounds of energy, but that would just be the way of things — let's face it, having an air powered rifle is better than having no rifle at all.

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The rifle pictured above is the Hatsan AT44-PA QE PCP pump action air rifle. The rifle seen above is only calibered for small rounds, but a scaled-up pump-action tactical air rifle design could be created. Image courtesy of pyramidairguns.com Heavy Weapons: Machine Guns: Thus far, a few manufacturers have made fully automatic air guns, but they all fire bullets of a relatively small caliber. Many manufacturers of air-powered paintball guns and BB guns make fully automatic models, yet these items offer such low muzzle energy that they are really just toys. The concept of making fully automatic machine guns that are powered by compressed is solid and proven, yet nobody has made the effort to turn these guns into anything more than novelty items — but that could easily change. Luckily, the only real change needed to make fully functional compressed-air-powered machine guns would be to take existing products and just scale them up a bit because the engineering, testing, and prototyping have already been done. An effective squad machine gun that gets its propulsion power from compressed air is a viable option, provided that the muzzle energy of the bullets thrown can rest above 800 foot-pounds on a consistent basis. Ideally squad-based automatic heavy weapons powered by compressed air would throw rounds that are 50—72-caliber or larger at speeds over 900 feet-per-second, and these weapons would also produce muzzle energy above 1000 foot-pounds on a consistent basis. Making heavy machine guns that get their power from compressed air is not as impractical as it may sound on the surface because these types of machine guns could be made much lighter on account of the lower muzzle pressures, and these weapons could also receive a continuous supply of air by way of a few larger air tanks and a portable compressor that is connected to the machine gun through a length of high- pressure hose. Having a continuous flow of compressed air available would also ensure

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that a compressed-air-driven machine gun would not be likely to overheat. Additionally, a heavy and fully automatic squad machine gun that is powered by compressed air would also be much quieter than a powder-burning heavy machine gun. For the sake of maintaining operator safety, the compressor and the storage tanks needed to drive a compressed-air machine gun could be kept many feet away, and the supply unit could easily be moved around on wheels out in the field, or the field- portable air supply unit could be carried by more than one man on shoulder poles if the terrain is too rough and uneven. There are presently a few manufacturers who produce small and light air pumps that are capable of continuously producing a flow of 4500-psi compressed air; additionally, these small air pumps are often paired with compact four-stroke piston engines that are typically used to power portable generators and yard appliances. Another option is to power the field compressors needed to keep pneumatic machine guns crooning with very powerful, light, and compact two-stroke piston engines that presently used to power chainsaws, weed-whackers, and leaf-blowers. Slam-fire mechanisms could also lend themselves to very rapid firing if they are fitted with a cranking wheel and a piston. Theoretically, a slam-fire mechanism would allow a shooter to actuate the loading mechanism by cranking a small wheel that would be mounted on the side of the weapon. The short bullet lengths associated with compressed air guns permit very rapid fire from slam-fire mechanisms because bullets that lack casings allow for 1—2-inch wracking mechanism movements, so this same principle would lend itself to rapid machine gun fire.

The image above is included to provide a reference for how a hand-cranked wheel could actuate a slam fire mechanism and permit very rapid shooting. Illustration courtesy of csharphelper.com

The wheel seen at left would have a handle attached that would allow the shooter to move the loading mechanism very rapidly by cranking.

The piston shown below would represent the wracking loading mechanism that would move back and forth loading and firing a bullet with each complete cycle.

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The weapon seen in the above photo is a fully automatic air-powered weapons that fires 22-caliber bullets at 600-feet-per-second. The weapons seen above draws its power from a hose connected to a backpack-mounted scuba tank. A photo of this product is included to show that fully automatic air-powered weapons are a proven concept. Image courtesy of fullyautomaticairgun.com

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The photo above shows the Air Ordnance model SMG .22-caliber fully automatic air gun. This air gun is belt-fed and is capable of firing rounds at around 600 -feet-per-second. The gun seen above does not have a straight-line type of design for the compressed air that moves the bullets, so there is somewhat limited power potential for this design; none the less, some manufacturers have managed to develop 50-cailber air rifles without straight-line firing designs that are capable of consistently producing over 700 foot-pounds of muzzle energy. Image courtesy of wideopenspaces.com

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The image above shows a World War II era training machine gun used by the American army. This air-powered training gun fired 30-caliber steel balls and was made by the Mac Glashan Air Machine Gun Corp, which was formed in July 1939 and closed in November 1943. The Mac Glasham company made several air-powered automatic guns that were sold as arcade diversions, but were pressed into military service as training guns. The photo above was posted to show that air-powered automatic guns are not a new idea. Image and information courtesy of forum.vinatageairgusngallery.com

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The American Air Arms 452 Slayer Bullpup rifle does not have a straight-line type of design for the movement of compressed air; unlike an Airforce Texan rifle, so there is less potential power; however, this rifle is still able to produce 700 foot-pounds of energy. Image courtesy of americanairarms.com

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The image above shows a close-up view of a revolver magazine for a 452-caliber American Air Arms rifle that is used in their 452 Slayer Bullpup rifles. Image courtesy of americanairarms.com

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The image above shows a small, compact, light-weight, and very portable piston engine and compressor combination unit that would be perfectly capable of keeping a powerful and fully automatic compressed-air-driven machine gun singing like Pavarotti and rocking like Led Zeppelin out in the field. A unit like the one seen above could also be fitted with a few carbon-fiber high-pressure air cylinders to act as a sort of uninterrupted power supply for the compressed air line in the same way that uninterrupted power supplies keep a computer working even after a power loss. A compressed-air-driven machine gun's portable power unit could also be outfitted with nice pushing handles and a rugged set of wheels to facilitate easy movement across many types of terrain. Image courtesy of daveychina.en.made-in-china.com Anti-Material Rifles For those who are unfamiliar with the concept, the term "anti-material rifle" describes large rifles that are designed to be fired from the prone position or from tripods, and antimaterial rifles typically shoot bullets that are 50-caliber or larger. International firearms laws generally define anti-material rifles as being any rifle that shoots ammunition that is 50-caliber or larger and produces a minimum of 10,000 foot- pounds or 13,600 joules of muzzle energy,15 although those numbers are regarded as arbitrary and debatable by many. Even though shooting bullets that 50-caliber or above defines what an anti-material rifle is, many anti-material rifles also shoot bullets that are over 20mm(82-caliber), and these rifles often have very long barrels.

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As listed on Wikipedia, anti-material rifles have been in use since the 1600s, and they have traditionally functioned as a middle-ground between artillery and regular rifles. Since the earlies days of muskets, tripod-mounted scaled-up versions of field muskets were used to attack artillery pieces and wagons along with troops that were out of range for smaller guns. In the 19th century, very large rifles that fired black powder cartridge ammunition were used for taking very long shots and disabling enemy equipment, and these rifles were called "Rampart Guns." Anti-material rifles were developed to destroy armored vehicles during World War I; however, as armor got thicker, these outsized rifles were increasingly used to destroy equipment and lightly armored vehicles. Due to their long range and effectiveness, these giant rifles have always been additionally used against individual people, so anti-material rifles essentially function as very large, super-sized, sniper rifles that have even greater ranges than regular sniper rifles. The phenomenal power of anti-material rifles also makes them a popular choice for shooting enemy combatants who are sheltering behind walls and other types of cover because the bullets launched by anti-material rifles are often able to punch through layers of brick, wood, and cement that are over a foot thick while still delivering lethal hits. As of the moment, nobody produces any compressed-air-powered anti-material rifles, but it would not be too hard to design guns like these that get their power from compressed air. Designing and building compressed-air-powered anti-material rifles is quite possible because these big rifles are really just scaled-up versions of common sniper rifles, and really good compressed-air sniper rifles already exist. So, in a practical sense, a compressed-air-driven anti-material rifle would just be a larger version of an Airforce Texan big bore-air rifle. Anti-material compressed air rifles would most likely be powered by either large air tanks connected to the back ends of these guns, or they could be powered by large hoses connected to good-sized air tanks that are kept nearby. Additionally, for the sake of maintaining safety protocols, any small compressors used to keep these guns chugging-along would probably be kept nearby, but not too close. Using compressed air as a driving force for effective anti-material rifles is certainly possible if these types of rifles are made to shoot even larger and heavier projectiles than their smokeless-powder-driven peers. Like with hunting rifles, compressed-air- powered anti-material rifles would have to use larger-caliber ammunition to compensate for their lower muzzle velocities, but acceptable results could be obtained with a little bit of compensation. Powering anti-material rifles with compressed air is actually not a bad idea because compressed-air-powered anti-material rifles would weigh less, produce less recoil, and make less noise than their powder-powered compatriots. Make no mistake about it,

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anti-material rifles that are powered by compressed air will still be long and somewhat heavy, and these guns will still produce a fair amount of noise and recoil, so all of the negative traits associated with anti-material rifles will still be present with compressed air anti-material rifles, just to a comparatively lesser degree.

The photo posted above shows a Chinese Jinjal rampart rifle from the 1880s. The rifle seen above fires 60-cailber cartridge ammunition designed to function with black powder as the propellant. This image is included to show that scaled-up versions of regular rifles and muskets have been around for a long time, and they have been used a midpoint between artillery and infantry rifles. Image courtesy of forgottenweapons.com

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The image above shows an American Revolutionary War Era amusette musket. Muzzle loading anti-material rifles usually fired bullets that were at least 50-caliber, but amusette rifles were known to be as large as 2-inches across in the barrel. During the days of George Washington, any gun with a barrel that was more than 2-inches in diameter was considered an artillery piece, as opposed to an amusette rifle. Photo and information courtesy of rev.ronv.net

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The image above shows a Sims-Dudley dynamite guns that was used by Teddy Roosevelt and the Rough Riders in the Spanish American War. The Sims-Dudley dynamite guns used compressed air to lob a 10-pound shells loaded with temperamental, but powerful, nitroglycerine-based explosives. Dynamite guns came into existence because cannon shells filled with dynamite, or other nitroglycerine-based explosives, had so much more destructive power than shells loaded with black powder. Compressed air was chosen as the propellant for launching dynamite and other nitroglycerine-based explosive artillery shells because launching these types of high explosives from a cannon that used gunpowder of any type would result in the shell exploding within the cannon's barrel. Only 18 Sims air cannons were ever purchased by the United States Army, and these cannons suffered from poor range and poor reliability when compared to black-powder-driven cannons of the same time period; however, this photo is included to demonstrate that producing large air guns is possible. Image and information provided courtesy of douglas-self.com

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The photo above was taken in 1885 and shows an air-powered Zalinski dynamite cannon. The United States Army bought dozens of Zalinski dynamite cannons and installed them as coastal defense equipment in several locations; however, high explosives that were able to survive a trip through a cannon's barrel without igniting were soon discovered and the old air-powered Zalinski guns were quickly scrapped. The cannon shown above was capable to hurling a 100-pound payload of dynamite more than two miles. Image courtesy of dawlishchronicles.blogspot.com

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The image above shows a few of the air cannons that compete at the Annual World Championship Punkin Chunkin event that happens on the weekend following Halloween every year. The Punkin Chunking competition happens near Bridgeville, Delaware. The air cannons seen above are capable of launching a 10-pound pumpkin over one mile by using air compressed to only 100-psi. So, yes, it seems quite possible to launch a 4,000+ grain bullet at over 900 feet per second by using compressed air. Image courtesy of eyeflare.com

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The image above shows a member of an informal militia using a home-made 23mm anti-material sniper rifle during the Syrian Civil War back in 2016. Anti-material rifles like the one shown above could be developed to fire large slugs by using compressed air. A compressed-air powered anti-material rifle like the one pictured above would probably have an even longer barrel and fire an even heavier bullet to compensate for its lower barrel pressure and lower bullet speeds. Image courtesy of thefirearmsblog.com

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The image above shows a home-built 23mm sniper rifle in action during the Syrian civil war in 2016. An anti-material rifle like the one shown above could be made to fire by using compressed air. Photo courtesy of imagur.com

Conclusion In a general sense, it is best to have access to smokeless powder and conventional firearms if the need for self-defense becomes quite pressing; however, it seems quite likely that supplies of conventional ammunition and the smokeless powder needed to drive conventional bullets could get scarce in the event of a societal breakdown. Supplies of smokeless powder and conventional ammunition could also get rather scarce for people who are on the receiving end of a deliberate attempt at genocide. Given the possibility that conventional ammunition could grow scarce if times get tough, it makes sense to have backup options available for pushing bullets out of gun barrels, and these back-up options for ways to move bullets include using black powder and compressed air. It seems that black powder is the first go-to option if supplies of conventional smokeless powder become scarce, but the problem with using black powder to propel bullets is that it takes a bit of time to produce black powder from scratch, so keeping a supply of compressed air guns around is also a good idea.

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Yes, in a general sense, compressed air driven weapons are not as good as their powder-driven counterparts; however, compressed air sniper rifles may be a total exception. At this time, the developmental work needed to produce solid defense-capable sniper rifles that are powered by compressed air is pretty much complete, and the air-powered hunting rifles that would make really effective sniper rifles are in fact so good that they should be viewed as a great choice even when regular smokeless ammunition is readily available. As for powering other types of firearms with compressed air, making anti-material rifles that are driven by compressed air seems like the next most promising application simply because anti-material rifles are just scaled-up versions of the compressed-air-powered rifles that are already sold on the market. Although making tactical rifles that fulfill the same functions as assault rifles seems possible, compressed-air-driven tactical assault rifles would still suffer from comparatively low shot counts and lower levels of power, plus these rifles would be a bit bulky, and they would require quite a bit of manual pumping to recharge. Given their inherent shortcomings, tactical rifles that run on compressed air should only be viewed as nothing more than back-up choices for rifles that fire conventional smokeless ammunition and black-power-burning rifles. Although no real developmental work has been done to design and build defense-capable compressed-air-driven machine guns, it seems quite possible to develop compressed-air-powered machine guns that would deliver an adequate level of field performance. It is not clear if compressed air machine guns would be a great first choice if regular machine guns that operate with conventional smokeless powder are available; however, it seems like machine guns that run off of compressed air offer some nice advantages over regular machine guns, and compressed air machine guns might actually be a great first choice for powering heavy weapons that are embedded in fixed locations. Some of the advantages offered by compressed air machine guns that are placed in fixed locations include being less noisy, not overheating, and not producing any noxious gasses. So, in conclusion, despite their faults, compressed air rifles are worth developing as a backup option for the tough times ahead.

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2. The Washington Times, "South's gunpowder 'war' ", July 30, 2005; thewathingtontimes.com

3. Bikram SINGH SEKHON, "history and basic principles of air rifles," November, 2010; researchgate.net https://www.researchgate.net/publication/320324028_History_and_basic_principles_of_air_rifles

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4. John Goodspeed, "Big Bore Air Guns" November, 2019; tpwmagazine.com https://tpwmagazine.com/archive/2019/nov/ed_2_airguns/index.phtml

5. Air Force Airguns "Prese Release January 2017" airforceariguns.com https://www.airforceairguns.com/Articles.asp?ID=348

6. Admin, " Calculating Barrel Pressure and Projectile Velocity in Gun Systems" February, 13, 2012, closefocusresearch.com http://closefocusresearch.com/calculating-barrel-pressure-and-projectile-velocity-gun-systems

7. Miles, "3D Printed Revolver", November 30, 2015, thefirearmsblog.com https://www.thefirearmblog.com/blog/2015/11/30/3d-printed-revolver/

8. Leo Greguric, "How Much Does a 3D Metal Printer Cost?" July 2, 2019, all3dp.com https://all3dp.com/2/how-much-does-a-metal-3d-printer-cost/

9. 8. Airgun Lab, " 2035 fps PCP Airgun Lab with extensive documentation" April 9, 2016; YouTube.com https://www.youtube.com/watch?v=qUq4OQqZ2bw

10. B.B. Pelletier, " Precharged pneumatic(PCP) airgun fears" February 12, 2010, pyramidair.com https://www.pyramydair.com/blog/2010/02/precharged-pneumatic-pcp-airgun-fears/

11. B.B Peltier, "What pressure is best for a PCP?" June 8, 2006, Pyramid Air Report, pruamidair.com https://www.pyramydair.com/blog/2006/06/what-pressure-is-best-for-a-pcp/

12. Bob Sterne, "Bob's guide to tuning unregulated PCPs" January 15, 2019, hardairmagazine.com https://hardairmagazine.com/ham-columns/bobs-guide-to-tuning-unregulated-pcps/

13. Kyle Mizokami, " A Secret? Is the U.S. Army's Go To Sniper Rifle Really Just a Hunting Rifle?" August 15, 2019, thenationalinterest.org https://nationalinterest.org/blog/buzz/secret-us-armys-go-sniper-rifle-really-just-hunting-rifle-73786

14. Bob Sterne, " Balanced Valves for PCP Airguns. They’re Here Today!", December 17, 2018, hardairmagazine.com https://hardairmagazine.com/ham-columns/balanced-valves-for-pcp-airguns-theyre-here-today/

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15. Mr. Chris Stevenson, Dr. Scott Wylie, "Offensive Weapons Bill, Session 2017-19" July 23, 2018, publications.parliament.uk https://publications.parliament.uk/pa/cm201719/cmpublic/OffensiveWeapons/memo/OWB95.htm