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MEMORANDUM REPORT NO. 1943COMPARISON OF THE EXTERIOR BALLISTICS OFTHE M-193 PROJECTILE WHEN LAUNCHED FROM
1:12 1IN. AND 1:14 IN.TW IST M16AI1R IFLES
4 Maynard J. lddlngtonDk October 1968
This document is ubject to special export controls and each transmittalr to foreign governments or foreign nationals may be made only wltn priorapproval of Commanding Officer, U.S.. Army Aberdeen Research and Development'Center. berdeen Proving Ground, Maryland.U.S. ARMY ABERDEEN RESEARCH AND DEVELOPMENT CENTERBALLISTIC RESEARCH LABORATORYABERDEEN PROVING GROUND, MARYLAND
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r(
B A L L I ST I C R ES E A R C I f LABORATOR I E SMEMORANDUM REPORT NO. 1943
OCTOBER 1968
COMPARISON OF THE EXTERIOR BALLISTICS OF TIlE.M-193 'PROJECTILE WHEN LAUNCIII'D FRO!I1:12 in. AND 1:14 in. TWIST ,MI16A1 RIFLES
Maynard .1. PiddingtonExterior Ballistics Laboratory
It
This document is ubject to special export controls and each transmittalto foreign governments or foreign nationals may be made only witn priorapproval of Commanding Officer, U.S. Army Aberdeen Research and DevelopmentCenter, Aberdeen Proving Ground, Maryland.
tRDT&E Project No. 1T6SO212D620
A B E R D E E N P R 0 V I N C G R 0 U N D, ? A R Y L A N D
A
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B A LL IS TIC ItE S LAR 1 L A tORItA T R IE S
MI;MORANDUM REPORT NO. 1943
I.Jriddington/ppAberdeen P'roving Ground, Md.October 19b8
COMPARISON OF THlE EXTEPIOR BALLISTICS OF TIMEM-193 PROJECTILE WHIEN LAUNChED FRM1:12 in. AN D 1:14 in. TWIST '116AI RIFLES
ABSTRACT
The results of an exterior ballistics tcst of the 4t-193ball projectile when launched from thc MlbAl rifle arepresented a'nd discussed. Rifles with twists of 1 turn in[12 inches and 1 turn in 14 inches were used in the tests.Data were gathered from test firings at the small AerodynamicsRange a~nd the Transonic Range of the Ballistic ResearchILaboratories and from a temporary range set up in theClimatic Hangar at the Eglin Air Force Base, Florida. Testsat Eglin were conducted at air temperatures ranging fromII, .125 deg. F to -65 deg. F.
3
7I77-- -- '-.-. ~ -. ~- --
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TABLE or CONTENTSPage
ABSTRACT .................................. 3TABLE or SY11BOLS................ . .... *...... 7INTRODUCTION ....... ....... .... ........ ***.. 9EXPLRIMENTAL PROCDU11L. ........ ........... 12
2.* Limit Cycle Test... ...... ....... .. *. 14LIMtITATIONS OFTIill.DATA .......................... 14
2. Rifles.................... .......... 16,3. Aerodynamic Characteristics ...................... 16
DLTLRNIINATION orRLSULTS ............................... 171. Velocity and Drag Force Coefficient... ....... 172. * Maximum Yaws........................ 17
S. Limit Cycle Yaw...... ... .............. 22b . physical Properties. . .. . .. . . .. . . .............. 23
DISCUSSION OF LESULTS.. . .... ............. . ..... 24
3. Stability Factor..................... 284. Dispersion. .. . ....... ~.. 286. Physical Properties .... .. ............. 3S7.* Twist Determinations... . ..... .. ... 45
CONCLUSIONS................................ 46
S
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TABLE OF CONTENTS (Continued).Page
REFERENCES .............................................. 50APPENDIX ................................................ 51DISTRIBUTION LIST .........................................9
I6
V
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TAIBLE Or SY~hI)LS
CDra& rorce
C, ,Static 'Ionent. *ClM (1l2)OV"Sict*C&U
*C C. Dimping :MomentJq a (1 /2) p ,2S..i
C ornal rorce( 1/ '2 o " SaaMlagnus NMoment1 a (1/2)pV 2 SE E a
= standard, deviation V:jo. of Observations -6 M agnitude of yaw6- Mean squared yaw over th e range of observationsS= lTd 2 /4P= air densitya angle of attack
. turning rates1,2
damping rates12geqative vatues o,4 C:,. and C: , + C,1 Zndicate ron,eita ,uh
o-.po~e a and & reapeetive.Zt! and are theteote atabZZzZinq.A poaitive vatue oA CT indZeates a Aide moment w',iehp1atJLiea to 'otatc the,LhC6e'.4a nose about it6 t4ajeeto4,r i.nthe direction o apin.
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TABLE OF SYMBOLS (Continued)
cg a center of gravityC.I. a Center of Impactd a body diameter of projectileIx axial moment of inertiaIy u transverse moment of inertiaK yawing vectors1 2A reference length (for this report L d a.223 inch)L = lcngth of projectileMt a Mach numberN = Twist rateo = subscript denoting initial conditionsp u rolling velocityq = angular velocityRd = round number212p
= V2 = gyroscopic stability factorI V2 d 30Cd C
SN = Serial NumberS a radius of swerveLV = velocity of missileWT a Weight
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INTRODUCTIONThe program reported is the Exterior Ballistics
portion of a larger effort involving several divisions ofth e Ballistic Research Laboratories (SrL). The program wascarried ou t in response to a request from th e Projecttanager-Rifles to evaluate th e relative effectiveness ofthe '1-16 rifles with barrels of two different twist rates;one turn in 14 inches of travel and one turn in 12 incl.esof travel.
The amount of spin required to stabilize a bulletdepends on various parameters, such as: bullet shape,muzzle velocity, air density and physical properties(including center of mass location, moments of inertia,etc.) A relationship of these various parameters,including spin, yields the gyroscopic stability factor, s,and fo r a projectile to be gyrosconically stable thisrelationship must he equal to or greater than one.
Mlost earlier small arms projectile designs have hadSvalues of s considerably greater than one, usually greaterthan two, and hence they were no t appreciably affected by
small variations in th e properties which influence thevalue of s. One might expect that variations in thephysical parameters, whether incurred during manufacture orlaunch, could causc a 10 percent variation in s. Inaddition, flight environrncnt, particularly air density, cancause a 25 percent dccrease in s when !oinp from 70 0I : to
* -(,S F. A projectile having a stability factor of 2 at 70oFwill not be seriously effected in its fl ight behavior when
. s drops to 1.35 fo r -05 0F.The %1-16 rifle system, however, launches a projectile
which has s values considerably below 2 and hence is much
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more susceptible to changes in air density and to othervariations in the parameters which dctcrminc s. For exanple,the gyroscopic stability factor of the !1-193 when launchedfrom the 'I-16Al rifle with a twist of one turn in 12 inches(1:12 in.) is about 1.45 at 700 F and decreases to a value ofabout 1.09 at -650 F. For th e same bullet launched from a1:14 in. twist barrel, s has a value of about 1.14 at 70Fand about .85 (theoretical) at -65F.* As the gyroscopicstability factor approaches unstable values, the flightcharacteristics of the bullet will deteriorate and coulddrast ical ly change. The main objective of the Lxterior.Ballistics Laboratory (1.BL) study was to determine preciselyhow serious an effect reduced values of gyroscopic stabilitywould have on thle flight characteristics of the projectile.
In order to perform this task, it was necessary formembers of the ELIL to travel to th e Air Proving Ground Centerat Eglin, Fla. to conduct a test of the ,4-LbAI in theClimatic Hangar where test temperatures ranging from 125 0 1.to - 6 5 F over a range of 70 meters were available. Tw o rifleswith 1:12 in. twist barrels and. two with 1:14 in. twists were
I0tested at five temperatures: 125, 70, 0, -30, and -65SF.It was desirable to use rifles which were currently
being produced by Colt Manufacturing Company, but this wa spossible only fo r th e 1:14 in. twist guns which were part ofth e "1000 barrel" tests.*** The 1:14 in. twist barrels hadbeen prorated, on th e basis of Colt tests, one as having"average" dispersion (7.5 in'. maximum spread at 100 yds) and
one as having good dispersion (4.0 in. maximum spread at100 yds). The 1:12 in. twist rifles were selected from th e
*Temperature effect on stability factor assumes standard sea levelpressure.**References are found on page 50.
***A special test to compare dispersion of the two twist rifles.10
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stock pile at AM', and were assumed to be typical of currentproduction rifles.
Since it was no t practical in thc time allotted forthis investigation to conduct separate studies on th e causesof the variations in th e parameters in s, it was necessaryto fire a sufficient number of rounds from each barrel ateach temperature so that the results would depict thesevariations. Fifteen rounds per condition were selected as acompromise between statistical desirabilities and availabletime. Fewer than fif:teen rounds were tested at 125 Fbecause of other test commitments of the lglin installation.The selection of th e 125F test cases for any necessarycurtailment was because of the probable lower relevance ofth e higher stability data.
The individual photographic equipment used in th e tests(2)were the same as utilized in the Aerodynamics Range atth e BIL. Ten shadowgraph stations using two orthogonal28 x 30 cm, plates were positioned over th e 70 meters and yawcards were placed at th e maximum range (70 meters) to recordth e dispersion.
Mteasurements obtained from the shadowgraph and yawcards were used to determine the following as functions oftemperature and twist:
1. Dispersion (a t approximately 70 meters).2. Muzzle velocity.3. First maximum yaw.4. Gyroscopic stability factor near th e muzzle.S. Maximum yaw at about 70 meters.6. Velocity at about 70 meters.7. Variations in 2, 3, 4, 5, and 6.
One month's test time (August '67) was required tocomplete th e firings with considerable assistance furnished
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by the personnel of the Climatic Hangar. After somemeasurements had been made and preliminary evaluationsconducted, it became apparent that additional data wereurgently required to permit th e WSL to conduct properlytheir phase of the evaluation. The magnitude of yaw atimpact often plays an important role in the analysis of asmall arms weapon system.- WSL requested that fl ight yaw atranges greater than 70 meters be obtained.
To obtain such data, five Aerodynamics Rangeshadowgraph stations were hastily assembled in th e(3)Transonic Range of BRL. 30 rounds were then fired, fromeach of two weapons (one 1:12 in. and one 1:14 in. twist)at ranges of about 175, 250, 340, and 450 meters. At theseranges, it was assumed that th e initial yaw transients haddamped out and that th e yaw remaining was due to somephenomena characteristic of the bullet. The data obtainedfrom these firings, as a function of range and twist (atapproximately 70 0 F.))were terminal yaw (commonly referred toas l imit cycle yaw ) and velocity.
For purposes of th e exterior ballistics portion ofthis report, these two tasks mentioned previously will bereferred to as:
1. Eglin Test.2. Limit Cycle Test.
EXPERIMENTAL PROCEDURE1. Eglin Test
Six stations observing aLout 5.79 meters of trajectorywere positioned near the muzzle of the gun (Figure 1). Fourstations covering about 3.3S meters of trajectory werelocated near th e target (70 meters). All stations werecarefully surveyed into position and then resurveyed at
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Figure 1. Station Setup at liglin
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various temperatures to insure that th e range had no t movedsignificantly because of a change in temperature. Ifchanges did occur, then necessary corrections to the datawere made.
The time of flight was recorded at eight of thestations (six in the first group and two in th e last). Inaddition to yielding velocity near th e muzzle and near thetarget, these were used to obtain a fair evaluation of th edrag force 'coefficient.
The. guns were separately mounted in a Frankford rest(Figure 2). The rounds were fired into a bullet catcherlocated behind the target. To protect th e equipment at th etaiget from being h it by stray rounds, a protectivebarricade' with about a 38 cm hole was placed directly infront of this group. All guns and ammunition were allowed'to temperature soak sufficiently before firing commenced..2. Limit Cycle Test
Five stations were used in this test located to observethe yawing motion over a period of either 2.74 meters (earlyphases), or 3.05 meters (later phases). Times of flightwere recorded on three of th e stations to yield velocity
Sdata.The guns were mounted in a Frankford rest. To obtain
data at the various ranges, th e gun position was movedrelative to the stations and a barricade was used to
* protect the stations from damage.' LIMITATIONS OF TIlE DATA
1. AmmunitionOnly one lo t of ammunition was used in all of th e EEL
tests. As a result, lot-to-lot variations are not14
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.NOT-REPRODUC"IBLE.
Figure 2. Frankford Rest with Rifle
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I.indicated in th e results. The ammunition used does nothave a specific production lo t number but is designated asLC-SP-412. The rounds were obtained from the productionline at Lake City Arsenal in June 1967. EBL was assured byth e office of the project manager that th e ammunition wouldmeet the necessary acceptance requirements.
LC-SP-412 is ball ammunition using ball propellant.It has not been determined how this lo t of ammunitioncompares to the other lots currently being used in theM-16AI rifle system.2. Rifles
"The 1:14 in. twist rifles were new and had very fewrounds fired from them (estimated as less than 100). The1:12 in. twist rifles used in th e tests were in goodcondition but much older, and no record was available onhow many rounds had previously been fired from them.
The number of rifles tested, of course, was extremelysmall and can not be confidently compared to an "average"1:12 in. or 1:14 in. production rifle.3. Aerodynamic Characteristics
In order fo r th e Computing Laboratory of BRL to obtainthe necessary velocity and yawing histories of theprojectile , a knowledge of the aerodynamic characteris t icsof th e bullet is required. Because of th e time frame ofth e program, however, only a limited new determination was(5)made with a basic reliance on earlier tests. The newdata obtained resulted from rounds launched in th e range atBRL from four rifles. Tw o of these rifles had a 1:12 in.twist and two had a 1:14 in.J twist. Tw o rounds were testfired from each weapon at standard muzzle velocity; thedata were reduced in the normal manner. The results are
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I
listed in Table 1 and can be compared to the results of apreviously tested round which can be found in Reference S.At standard muzzle velocity, the data agree quite well withthe data in BRL MIR 1758 with only one apparent exception.The overturning moment coefficient, C,,, fo r th e LC-SP-412around is about 8 percent larger than previously determined.-This causes a decrease in the stability factor and is anindication of the variability from lot-to-lot in theammunition.
DETERMINATION OF RESULTS1. Velocity and Drag Force Coefficient (Eglin Test)
The velocity, ., and drag force coefficient, CD9 wereobtained for each round from a least squares fit of time asa cubic in distance. These values were computed at a pointapproximately 4.6 meters in front of the rifle. Thevelocities were then extrapolated to yield muzzlevelocities.
For various reasons, time measurements were not alwaysrecorded in the second group of stations. Ilithout thislonger-base-line data, drag computations were not veryaccurate. Such rounds, as a rule, produced no drag ordownrange velocity data.2. :taxinum yaws (Eglin Test)
The first maximum yaw, 6 max, and the maximum yaw,max. at about 70 %eterswere obtained from faired curvesof the total yaw as a function of range. A typical example
of such curves is shown in Figure 3. The measured valuesare represented by th e circles which could include a pointat th e rifle muzzle. Although no shadowgri-phs were takenat this position, it is reasonably safe to assume that theyaw at this point was very nearly zero.
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CD
CD
c'JMVI) 04J
LL 0
cr.0-IZ
0 (0L
.O4
018
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Figure 3 indicates the magnitudc anid location of thefirst maximum yaw and the period of yaw ner the muzzle.Also indicated is the magnitude of the minimum yaw near themuzzle which is very nearly zero for this round and fornearly all other rounds tested, regardless of the magnitudeof the first maximum yaw.
At 70 leters, the maximum, minimum, and sometimes theperiod of yaw are indicated. At this range, the minimum yawis most likely not zero. Because of the aerodynamic and(5)dynamic characteristics, the nutational node of yaw isdamping much more rapidly than the precessional mode. It isprobable that only the precessional yaw remains and this modemay be slowly damping, remaining constant, or even slowlygrowing. An insufficient number of observations were made atthis location for a complete determination of the yawcharacteristics. Only an average approximate position of themaximum yaws can be given both at the gun and at 70 meterssince these positions vary by as much as several feet from.round to round.3. Stability Factor (1h".lin Test)
The stability factor, s, was determined from the yawingnotion of each projectile using only the yaw observed in thefirst group of stations together with an assumed value ofzero yaw at the muzzle. Since only the epicyclic turningrates arc required to determine s, the yaw equation wa sslightly modified so that these values could be easilyobtained.
In addition to s, values of the overturning momentcoefficient, CH , and the twist rate, N, imparted to the
abullet were determined for each round. In determining C,aand the twist rate, average values of the moments of inertia19
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were used since it would have been impossible to obtain thesevalues fo r each round tested. Consequently, CH and Nareflect th e variation in moments of inertia. s on th e otherhand, is a true indication of the stability factor asdetermined from th e yawing motion of each round. All threevalues were determined at a point located about 4.6 meters in'front of the gun.
This method of analysis can be used with confidence onlywhen the stability factor is grcater than i. 1Ihen so is lessthan 1, the projectile is initially unstable. The yawhistory becomes abnormall y high but otherwise often appearssimilar to that of a' stable 'bul let because high yaw phenomenacontrol th e instability. The linearized yaw equation useddoes not recognize these effects and,. in fitting,'ascribes to"the motion a pseudo value of s slightly larger than 1. Sinceth e linearized assumptions used in. the fit are obviouslyviolated, no reductions were performed on those, rounds whichhad theoretical s values less than unity. Careful considera-tion must be given to those determinations yielding s valueswhich lie between 1 and about 1.1 to make sure that theserounds were not, in fact, initially unstable.,
An example of such a round is shown in Figure 4. Eventhough the period of yaw is apparently quite large, thegeneral yawing motion is such as to indicate that th e bulletis gyroscopically stable, which fo r all practical purposes,it is, ou t no t initially. The bullet emerg.ed from the barrelwith insufficient spin to stabilize it and soon thereafterstarted to "tumble". It never completed this motion for as,th e yaw began to grow it became, less unstable unti l finallys was larger than 1. With s ' 1, the yawing motion went intoan apparently normal epicyclic motion. The result of thisinitial instability was an increased yaw and a probableincrease in dispersion.
20
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0I0'.1A
w .0.
2 -U) 0 -
0 0 a0
21.
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4. Dispersion (Eglin Test)Dispersion calculations were performed on data in two
ways. The first was to use only those data observed fromth e photographic station located at about 69 meters. Thisdetermination was made on 15 rounds fo r each condition. Thesecond was to perform th e calculation on measurementsobtained from yaw cards at about 70 meters which, in general,was for about 10 additional rounds fired with no photographiccoverage fo r each condition. Then both sets of data werecombined to yield a value fo r 25 rounds. It seemed importantto handle th e data in this manner since the 10 round groupswere obtained in a period of about S minutes whereas th e 15round groups covered a period of time of several hours.However, it was concluded that the differences observed fromthese methods were insignificant and that the value whichwas obtained for all 25 rounds was most representative ofthat rifle.
It should be noted that although some rounds hitth e protective barricade, these misses were not excluded;hits were marked and by extrapolation were included in th edispersion calculations.5. Limit Cycle Yaw (Limit Cycle Test)
The yaw was determined at each of the 5 photographicstations and then averaged to represent th e value of the
Slimit cycle yaw. It was assumed that all initial transientyaws had damped before the round had reached th e stations,even fo r th e closest distance used in this test series (175meters). Data were obtained at three additional ranges:253, 33 , and 450 meters. Thirty rounds were fired fromeeach o two rifles (one 1:12 in. twist and one 1:11 in.twis at each range.
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Velocity measurements were also recorded fo r eachround. These values were adjusted since the guns werefired at different temperatures. The photographic stationswere positioned in the Transonic Range, which is heated to
0about 70 F, but the guns were located outside th e rangeexcept fo r the 17S meter range. The temperature at thetime of firing varied from 35 to about 700F. Correctionswere made based on the muzzle velocity vs temperature dataobtained at lglin.6. Physical Properties
When values of the physical properties are required tocompute certain aerodynamic characteristics, it is highlydesirable to use those properties which pertain to eachround. Normally, for large shell, measurements areperformed on th e rounds before they are launched. In thecase of deformable bullets, the characteristics are l iableto change when the round is fired so that if prefiringmeasurement values are used, at least slightly incorrectresults will be obtained. As a precaution, it was decidedto obtain sample values of these physical measurements onproject i les which had sustained changes due to normalfiring.
j The EBL has unpertaken th e tasks to determine thechanges in the bullet (particularly LC-SP-412) due tolaunch, but all of the results are not available fo r thisreport.
Past experience has indicated that in order to recoverthe bullet without damage with current recovery systems th ebullet should have a velocity no t much greater than about365 m/s. Since measurements should be made on rounds which
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have b-een launched at standard muzzle velocity,* th erecovery system had to be placed about 600 meters fromth e gun.
A recovery system composed of foam rubber which wassaturated with water was used. A depth of about 1.83meters was required to stop the bullet. Ton rounds werefired from a 1:12 in. twist rifle, recovered, and measured.In addition, te n rounds were measured before launch andthen recased and fired from the same gun, recovered andthen remeasured. This procedure compares before and aftermeasurements on th e same round. These measurements involvemoments of inertia, center of mass, length, and diameter.These data are available for-this report but results ofmeasurements made on th e contour of the prbjectile beforeand after launch are not available at this time. There a-retwo observations on shape changes that can be stated.First , th e boattail appears to open up slightly, resemblinga square base. Second, the ogive appears to cave in justahead of th e shoulder with a slight bulging of the ogivejust ahead of the depression.
DISCUSSION OF RESULTSThe data resulting from the various tests are presented
in tabulated form in the appendix in the following manner:
*Atternate methodh o6 4iiZng at 'teduced vetocity maty notproduce Autt deto'wation, atthough th e method i,& cet ta inyLan impkoveient over a-sing ungired piLojectiLe6. In gact,att thee digfetenea matt u6uatty be irrelevant but it wa&6eUt nece6AaAy to conaLcZ the teit to be 6uke.
24
Ii _ __ __ _ _ _ _ ___.___.__ _"._ __ ___._
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Table I Results of the Eglin TestTable 2 Results of the Limit Cycle Yaw TestTable 3 Dispersion (i:glin Test)Table 4 Summary of Aerodynamic CoefficientsTable 5 Physical PropertiesTable 6 Average ResultsThe remaining portion of this section will deal
primarily with the average results presented in the tables.If differences between weapons are of interest, then th etables should be examined.1. Velocity (Table 6)
The average muzzle velocity is plotted in Figure 5 asa function of temperature. The curves indicate that at125 F the muzzle velocities of th e 1:12 in. twist and1:14 in. twist weapons ate th e same. As th e temperaturedecreases, however, V fo r th e 1:14 in. twist riflesdecreases at a more rapid rate than does V fo r the 1:12 in.twist rifles until at -65 0 F they differ by about 21 m/s.In general, V decreases by about 84 m/s over the0* temperature range tested. Also included in Figure 5 arethe velocities determined at 70 meters fo r th e sameconditions for which V0 was determined. These curvesindicate that at the warm termperatures the loss in velocityfor each weapon is about the same. At -b 5 F, however,rounds fired from th e 1:14 in. twist rifles lose about61 m/s more titan those fired from 1:12 in. twist rifles.The reason for the increase in velocity loss is theconsiderable increase in yaw which adds to th e drag.2. Yaw (Table 6)
The average first maximum yaws for each rifle areplotted in Figure 6 as a function of tenperature. It canbe seen that the initial yaws for the two rifles are about
25
* ____________________________
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2 ..
cr.O
I--LL . 140o
LUL
4JJ
> 00SCD.
26~
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th e same at 125OF but differ considerably at -65F. 0 'forth e 1:12 in. twist rifle changes very little over thetemperature range test while 6 fo r th e 1:14 in. twistrifle increases from about 6 degrees at 12SF to about36 degrees at -65F. Also included in Figure 6 are the.maximum-yaw values determined at about 70 meters for eachrifle. These values have about the same magnitud.e at thewarmer temperatures but still differ significantly at
60 a-65F -- about 3 degrees fo r the 1:12 in. twis~ t rifles andabout 9 degrees for th'e 1:14 in. twist rifles..3. Stabili ty Factor (Table 6)
The average stability factor, s, fo r each weapon isplotted in Figure 7 as a function of temperature. Stabilityfactors were dctermincd at all temperatures for~the 1:12 in.twist rifles whercas s was determined at only 70 and 0degrees fo r the 1:14 in. twist rifles. It would have beenpossible to obtain s at 125 F but insufficient test data atthis temperature negated this determination. At 0 F andbelow, however, it is impossible to determine s accurately'using linearized assumptions, but it can be adequatelycomputed using data obtained at another temperature or bydata obtained from another twist. Those portions of thecurves shown as dotted l ines were computed in this manner.The value of s determined at 125F for the 1:12 in. twistrifle is slightly higher than is predicted. The reason forthis difference is no t apparent.4. Dispersion (Table 6)
The dispersion, a, is plotted as a function oftemperature in Figure 8. Each point represents a weightedaverage combining the results of two 25 round gToups (onegroup from each rifle). The value for each 25 round groupwas obtained using one center of impact. All rounds within
28
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IL.
CA.
-I-
cm* . . .
In4J0) C
-. -4
... L.o29I
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a 25 round group were fired from a single gun location but10 rounds were fired over a short period of time(approximately 5 minutes) while IS rounds using photographiccoverage required four hours or longer to fire. Hence, itis possible that differences in dispersion exist because ofth e time involved to complete each phase of the test.Figure 8 treats the data as though these differences arenegligible. Individual results can be examined in Table 4.
Basically, the dispersion of both rifles is about th esame for the warmer temperatures. At colder temperatures,a begins to worsen for the 1:14 in. twist rifle until at.- 65 F it has become about 4 times greater than a for the1:12 in. twist rifle, which is relatively unchanged. Theincrease in dispersion begins when th e stability factornears 1. This occurs at about 400F with th e 1:14 in. twistrifle and at about -45F with the 1:12 in. twist rifle.S. Limit Cycle (Table 2)
The distribution of the l imit cycle yaw is shown as afunction of range in Figure 9 fo r th e 1:12 in. twist rifleand Figure 10 for the 1:14 in. twist rifle. It wasintended that th e data be obtained at 70F but th etemperature could not be controlled for the three longerranges since the guns were outside the Transonic Rangebuilding. The temperatures outside of the building variedfrom 35 to 70F. At th e 175 meter range, th e guns weremounted inside th e building which is normally temperature-
* controlled to about 70F. The effect of coldertemperatures is a slight decrease in muzzle velocity fromboth rifles and in th e case of the 1:14 in. twist rifle, aslight increase in initial yaw (not measured in this test).It is felt that the magnitude of the observed yaw at thephotographic stations was not significantly changed by th e
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increased initial yaw, because all rounds, regardless ofdistance fired, traveled through about 200 meters of 700Fair in th e Transonic Range before being photographed.Recordings obtained fo r the 1:14 in. twist rifle and forsome of the 1:12 in. twist rifle rounds are for velocit ieswhich are slightly lower than if th e rounds had beenlaunched at 70 0 F.
"It should be noted that at 450 meters, only about50 percent of the rounds launched from the 1:14 in. twistrifle negotiated th e protective barricade. There arethree equally important reasons fo r this inaccuracy..'First, th e 1:14 in. twist rifle normally has slightlypoorer dispersion than th e 1:12 in. twist rifle under thesame conditions. Second, the dispersion of the 1:14 in.twist rifle increases slightly because of higher initialyaws which th e 1:12 in. twist rifle did not experience.Third, th e rounds launched from both twist riflesexperienced a strong cross wind (about 150 meters beforeentering still air) which appeared to have a significantbearing on th e rifles' accuracy.
The curves in Figures 9 and 10 indicate th e sameapproximate trends. The major difference occurs at 175meters where th e yaw from th e 1:12 in. twist rifle isconsiderably less than from the 1:14 in. twist weapon.Tw o reasons are apparent for *this difference. First,larger initial yaws from the 1:14 in. twist rifle willcause slightly higher yaws at this range. Second, becauseof these higher initial yaws, slightly more velocity willbe lost , with th e same effect as obtaining 1:14 in. twistdata further downrange. This is apparent upon examinationof the data as a function of velocity instead of range.Since th e l imit cycle yaw is increasing quite rapidlybetween 175 and 250 meters, a decrease of about 23 m/s in
34
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the velocity of the projectile should significantly Increasethe magnitude of the limit cycle.
After about 175 meters of travel, little additionaldifference in velocity should be expected. The magnitude ofyati beyond 175 meters appears to be slig]itly higher for the1:14 in. twist rifle with a slight upward trend occurrin, at4S0 meters. If the data are examined as a function ofvelocity, this upward trend occurs fo r bothi twist rifles hutis slightly more apparent with the 1:14 in. twist weapon,mainly because the projectile has slightly less velocity at450 meters.
The probable reason why the upward trend occurs fromeither weapon is thc fact that the projectile is rapidlyapproaching the transonic region. Although no data on thisprojectile arc availible to substantiate this conclusion,other data do ", st on a prototype model (unpublished) anti(6)on th e 'H-80 ball projectile which strongly suggest thatl imit cycles larger than two or three degrees will existbelow Mach 1. Therefore, it is quite conceivable that the.1-193 bullet will begin to respond to this effect by 4S0meters.
Figure 11 is a plot of the velocity of the projectileas a function of range and twist. All velocity values have
0been adjusted to the expected value at 70 F. The curves area compilation of data obtained at Eglin and at theAerodynamics and Transonic Ranges.U. Physical Properties (Table 5)
Only a limited amount of work has currently beenperformed on determining the physical changes in a bulletcaused by forces at launch. Bullets have been measuredprior to and after launch; the results of these measurementscan be compared in Tablc--.-
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The measurements that have been conducted indicate thevariations in the physical parameters and the changcs inthese parameters due to launch. lWhile nost of the changesor variations are small (on the order of 2 or 3 per cent orless), the resultant error of combinations of theseparameters, such as used fo r spin calculations, can beconsiderably larger.
Some of the more subtle changes which occur duringlaunch are those which physically change the shape of bulletsand are much more difficult to measure: such changes asloss of copper, damage to the jacket, distortion of theboattail section, etc. It is sometimes difficult to observethese changes with the naked eye but they can often be seenin the shadowgraphs of the projectile in flight.
Several enlarged shadowgraphs are presented (Figures 12through 18). The pictures encompass firings at variousconditions. If the reader will note that any sudden changein the contour of the projectile will produce a shock wave,it will become immediately obvious that the projectile haschanged considerably during launch. A brief description ofeach figure is given below. While it is left to the readerto decide as to the degree of damage which may be observedin the figures, his attention is invited to the flow aboutthe projectile as a function of yaw. It should be notedthat as the yaw increases, the prediction of certainaerodynamic characteristics becomes more difficult.
Figure 12: A round fired at -65 r from a 1:14 in. twistrifle. The angle of yaw is about 30 degrees. Note that theflow has leeward separation at the nose.
Figure 13: A round fired at -65 F from a 1:14 in. twistrifle. The angle of yaw is about 25 degrees. Note that theflow separation point has moved rearward to about theposition of the shoulder.
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,A
Figure 12. M-193 at - 650FV= 70m/s 6=300
. 38
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41 ItI
Figure 13. M-193 at -65 FV =925 m/s 6=250
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VU..
Figure 14. M-193 at -65 FV 910 M/S =100
40
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'!7 -
s r,~ :.
Figure 15. M-193 at 1250FV =965 m/s 6100
41
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77`1t -7
IT
Figure 16. M-193 at 1250FV 995 m/s 6 1
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Figure 17. M-193 at 7Q0FV =472 m/s 62.50
____ _______ _ __ ___ ____ ____ _____43
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7!j-, 7:7777T
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Figure 18. M-193 at 70OFV 455 m/s 62.50
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Figure 14: A round fired at -65F from a 1:12 in.twist rifle. The angle of yaw is about 10 degrees and theflow now separates at about th e position of the crimpinggroove.
Figure 15: A round fired at 12SF from a 1:14 in.twist rifle. The yaw angle and flow separation positionare about the same as in Figure 14.
Figure 16: A round fired at 125F from a 1:14 in.twist rifle. The angle of yaw is less than one degree.The flow has turned the corner of th e boattail .
Figure 17 and 18: Pounds photographed at about 700Fat a velocity of about 457 m/s. Both rounds were firedfrom a 1:14 in. twist rifle. The rounds have l imit cycleyaws of about 2.5 degrees.7. Twist Determinations (Table 1)
Computations of th e rifle twists have been made foreach round fired at Lglin. A knowledge of the yawing motionand th e moments of inertia are required to compute thesevalues. Since it was not possible to obtain moments ofinertia for each round fired, the average value obtainedfrom recovered rounds was used fo r all rounds; hence, th evariations in th e twist values given in Table 1 are onlytrue if th e values of the average moments of inertia areprecisely those ascribed to the bullet , which is not thecase. On th e other hand, averaging several twist valuesshould yield a representative value of the spin imparted toth e bullet . The nature of th e yawing motion of thisprojectile is such that th e spin will become less welldetermined as the stability factor approaches one.
The average values of twist computed in this mannerare 1:11.9 in. for th e 1:12 in. twist rifle and 1:13.5 forthe 1:14 in. twist rifle. These numbers are evaluated at a
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point 4.57 meters in front of the muzzle and should beincreased by about .08 in. to give muzzle values. Agreementis quite good for the 1:12 in. twist computations whereascomputations fo r the 1:14 in. twist rifle indicate that therifle imparted more spin to the bullet than the rifling had.The difference is on th e order of 2 or 3% and could easilybe accounted for by the reasons previously mentioned.
In order to determine conclusively the spin imparted tothe bullet , measurements of the spin of the bullet in flightshould be made and extrapolated to the muzzle, This can bedone to an accuracy of less than .1. by fitting theprojectile with pins in the base before- launch and measuringtile orientation of these pins as a function of range. Fiverounds have been tested from one rifle in this manner butth e results are not available at this time.
Oite DMPS at 'Aberdeen measured the twist of rifling of120 rifles (bO 1:12 in. twist and 60 1:14 in. twist rifles).;Ieasitrcm:nts were recorded at 1 inch intervals along th etube. The method and results of these measurements aregiven in Reference 7. In addition, the four prime riflesused in th e 1I1L tests w'zere measured; th results arepresented in Figures 19 and 20. It is noted that them.easutred values do no t forn a snooth cUrve so it is"diffi ult to determine th e precise tv..ist at the time theb)ullet becomes disengaiged fron the rifl ing.
COiNCLS I0NS '1. 1i1e M-193 projectile when launched from a .1 in 12 inch
Sti.ist tube is gyroscopicallystable at the atmosphericdensit ies consistent w:ith military test temperaturesranging.from 125F to -6501.
46
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2. The M-193 projectile when launched from a I in 14 inchtwist tube is gyroscopically unstable at the atmosphericdensities consistent with m ilitary test temperatures ofbelow about 0OF.'
3. Both twist weapons produce about the same initialmaximum yaw at normal air density and below (yaw fromth e 1:14 in. twist tube is slightly larger). At thehigh density condition (-65 F) the 1:14 in. twist weaponproduces about 360 of yaw as compared to about 80 yawfrom the 1:12 in. twist rifle.
4. The dispersion is about the same fo r each twist at normalair' densities (the 1:14 in. twist being slightly larger)with the dispersion of th e 1:14 in. twist weapon beingconsiderably worse at the high density cold temperatures.At th e -6OF test point, these values are about 2.4 milsfor the 1:14 in. twist as compared to about .6 mils forth e 1:12 in. twist rifle.
5. Terminal yaw of the Mt-193 projectile when launched fromeither weapon varies from nearly zero yaw to about 3.5degrees. Generally, th e yaw obtained from the 1:14 in.twist rifle tested was slightly larger than that fromthe 1:12 in. twist rifle for the same range.
6. The sample of the current M1-193 projectile productionused in the test receives a certain amount of damageduring launch. The boattail and ogive sections appearto be the areas most affected.
7. In-bore and aerodynamic spin measurements indicated thatth e r if les-with the 1:14 in. twist had twists which werefaster than 1:14 (on th e order of 1:13.8 inches) whileno significant difference was observed in 1:12 in. twistrifles.
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REFERENCES1. Brochure, Climatic Laboratory Facilities Air Force
Systems Command, Eglin Air Force Base, Flor'da.2. W. F. Braun, "The Free Flight Aerodynamics Range",Ballistic Research Laboratories Report No. 1048,
July 1958, AD 202249.3. W. K. Rogers, Jr., "The Transonic Free Flight Range",Ballistic Research Laboratories Report No.. 1044,,
June 1958, AD 200177.4. C. II. Murphy, "Free Flight Motion of SymmetricMIissiles", Ballistic Research Laboratories Report
No. 1216, July 1963, AD 442757.5, . J. Piddington, "The Aerodynamic Properties of a
Caliber .223 Remington Bullet Used in ?116 (AR-lS)Rifle", Ballistic Research Laboratories MemorandumReport No. 1758, June 1966, AD 489960.
6. M. J. Piddington, "Aerodynamic Characteristics of the7.62mm NATO Ammunition Mf-59, 1-80, M1-61, H-62",Ballistic Research Laboratories Memorandum ReportNo. 1833, March 1967, A D 815788.
7. II. fI. amison, "Test of 120 Rifles - 5.56mm M16Al.60 Rifles with a Basic Twist of 1:12.0 in. and 60Rifles with a Basic Twist of 1:14.0 in.", PhysicalTest Laboratory Report No. 68-8-15.
50
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APPENDIXTABLES
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TABLE 2A RESULTS OF TIHE LIMIT CYCLE TESTRifle SN 023199 (1:12 in. Twist)
175 Meters 253 MetersRd. L.C. V Rd'. L.C. VNo. (deg.) (ft/sec) No. (deg.) (f t /sec)40 2.1 2559 86 2.8 2162,41 .5 2557 87 .4 219342 1.6 2546 88 .6 214843 .2 2521 89 1.3 216344 .6 2525 90 .2 221647 .2 2495 92 1.3 217848 .3 2571 93 .3 .217549 .3 2596 .94 2.2 220650 .3 2512 95 1.5 219851 .4 2556 96 2.0 2166
8316 .5 2515 8353 2.4 19868317 .2 2500 8354 .4 21458319 .2 2510 8355 .2 21828320 .7 2520 8356 2.4 22128321 .3 2560 8357 .4 21638323 .4 2530 8358 .3 21668324 1.3 2565 8359 1.9 21388326 .4 2531 8360 2.0 21538327 2.2 2455 8361 2.2 20948483 .3 2543 8362 .3 21768484 .2 2569 8386 2.3 21928485 .3 2621 8387 2.3 21938486 .1 2540 8388 1.4 --8487 1.3 2562 8389 2.4 21488488 .8 2547 8390 2.3 21768489 2.1 2506 8391 .2 22038490 1.8 2517 8392 .3 21758491 .2 2534 8393 2.2 21198492 .2 2513 8494 2.0 21478493 .8 2573 8395 .5 2177
Avg. .69 2538 Avg. 1.37 2164
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TABLE 2A .RESULTS OF TIHE LIMIT CYCLE TESTRifle SN 023199 (1:12 in. Twist)
(Continued)
S339eters 45 0 MetersRd. L.C." V Rd. L.C. VNO . (deg.) (ft/sec) No . (deg.) (ft/sec)
2 2.0 1929 72 2.5 15513 .2 1938 74 1.4 --4 2.0 1927 75 2.9 15185 .3 1943 76 2.4 15606 2.2 1900 77 3.1 14528 2.7 1918 78 2.3 1507"9 2.3 1956 81 2.5 154910 .3 -- 82 3.1 146311 2.0 1909 83 .8 1574
12 2.6 1905 84 2.7 15088420 2.3 1872 85 .6 15788421 .3 1884 8397 2.0 15178422 1.6 1887 8398 2.7 16178423 2.2 1865 8399 2.6 15998424 2.1 1909 8400 2.9 15258425 2.3 1877 8401 2.5 15318426 .3 1917 8402 2.5 15348427 1.6 1891 8403 1.9 15708428 2.2 1879 8404 2.2 14728429 2.2 1871 8405 2.2 14448430 2.4 1896 8407 2.5 14S58431 2.4 1912 8408 2.8 15958432 .2. 1925 8409 2.5 15278433 2.2 1858 8411 .2 15788434 2.4 1900 8412 2.5 15878435 1.2 1867 8413 2.9 15438436 .2 1901 8414 2.4 15298437 2.1 1903 8415 2.9 15188438 .2 1923 8416 2.4 15158439 2.4 1909 8417 1.8 15898418 2.3 1575
8419 2.4 1502
Avg. 1.65 1902 Avg. 2.29 1535
7A4
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TABLE 2B RESULTS OF THE LIMIT CYCLE TESTRifle SN 789076 (1:14 in. Twist)
175 Meters 253 MetersRd. L.C. V Rd. L.C. VNo. (deg.) (ft/sec) No. (deg.) (ft/sec)8330 1.8 2483 103 3.6 21288331 2.1 2520 105 2.9 19978332 2.4 2485 106 2.2 20328333 2.2 2447 107 2.7 21418334 2.4 2341 108 2.5 21038335 2.4 2466 109 2.1 21338336 3.4 2408 110 1.8 21828338 2.3 2360 111 2.2 21288339 2.4 .2474 112 2.2 21858340 .2 2468 113 2.5 21168341 3.1 2384 114 3.1 20178342 2.9 2415 8363 2.6 21418343 2.1 2465 8364 2.6 21408344 o4 2490 8365 1.8 21388345 1.4 2496 8366 1.5 21508346 2.2 2407 8367 2.6 20678347 .6 2490 8368 2.4 20518348 2.4 2455 8370 2.4 20269349 2.2 2487 8371 2.6 19948350 2.2 2417 8372 2.2 20378351 .4 2473 8373 2.1 20518352 2.1 2501 8375 2.1 21258473 2.4 24S5 8376 2.9 21268474 1.9 2520 8377 2.4 20868475 1.5 2504 8378 1.2 21248476 2.3 2495 8379 2.5 21868477 .6 2501 8380 2.6 21958478 .8 2470 8382 2.3 22058479 2.4 2496 8383 1.7 21158480 3.0 2496 8384 2.6 20558481 2.1 2485 8385 2.0 21948482 2.1 2444Avg. 1.96 2462 Avg. 2.35 2109
75
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TABLF 2B RESULTS OF TIlE LIMIT CYCLE TESTRifle SN 789076 (1:14 in. Twist)
(Continued)
339 Meters 450 MetersRd . L.C. V Rd. L.C. VNo. (deg.) (ft/sec) No. (deg.) (ft/sec)33 2.4 1839 8466 3.3 144935 2.5 1785 8467 1.5 146437 2.8 1858 8468 3.1 139238 3.3 1900 8469 2.8 141839 2.1 1846 8470 3.2 1478
8440 2.7 1828 8471 2.6 14358441 2.3 1902 8472 3.1 14578442 2.3 1805 8494 3.2 14258443 2.4 1906 8495 .2 15408444 2.3 1764 8496 3.0 14888445 2.4 1819 8497 .4 15218446 2.4 1815 8498 2.7 14908447 2.2 1844 8499 3.0 14658448 2.9 1748 8500 3.0 15258449 2.9 1792 8501 2.8 14078450 1.6 1839 8503 3.0 14598451 2.S 1831 8504 2.7 15208452 2.6 1758 8505 3.4 1499S8453.6 1821 8506 2.8 14948454 1.9 1858 8507 2.8 14658455 2.4 1806 8508 3.5 1463845b 2.2 1750 8509 3.3 15218457 3.0 1788 8510 2.9 15078458 2.4 1812 8511 3.5 14548459 2.4 1797 8512 2.6 .14808460 2.6 1792 8513 3.4 149484b1 2.8 1813 8514 2.0 14838463 2.6 1813 8515 2.4 15698464 2.5 1748 8516 -- 15098465 -- 1834 8517 3.3 14918518 2.1 1532
8S19 3.3 1526Avg. 2.48 1817 Avg. 2.74 1482
76I _ __ _ _ _ _ _ _ _ _
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TABLE 2C RESULTS OF TIlE LIMIT CYCLE TESTVelocities Corrected to 70FRifle SN 023199 (1:12 in. Twist)
175 Meters 253 MetersRd. V Rd. VNo. (ft/sec) No., (ft/sec)40 2559 86 216241 2557 87 219342 2546 88 214843 2521 89 216344 2525 90 221647 249S 92 217848 2571 93 217549 2596 94 220650 2512 95 219851 25S6 96 21668316 2515 8353 20218317 2500 8354 21828319 2510 8355 22208320 2520 8356 22518321 2560 8357 22018323 2530 8358 22048324 2565 8359 21758326 2531 8360 21918327 2455 8361 21318483 2543 8362 22148484 2S69 8386 22308485 2621 8387 22318486 2540 8389 21868487 2562 8390 22148488 2547 8391 22418489 2506 8392 22138490 2517 8393 21568491' 2534 8394 21848492 2513 8395 22158493 2573
Avg. 2538 Avg. 2188
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TABLE 2C RESULTS OF THE LIMIT CYCLE TESTVelocities Corrected to 700 F
Rifle SN 023199 (i:12'in. Twist)(Continued)
339 Meters 450 MetersRd. V Rd. V,No. (ft./sec) No. (ft /sec)2 1929 72 15513 1938 75 15184 1927 76 1560S 1943 77 14526 1900 78 15078 1918 81 15'499 1956 82 146311 1909 83 1574
12 1905 84 15088420 1900 85 15788421 1913 8397 15408422 1916 8398 16428423 1894 8399 16248424 1938 8400 15488425 1906 8401 15548426 1946 8402 15588427 1920 8403 15948428 1908 8404 14958429 1900 8405 14668430 192'5 8407 14778431 1941 8408 16208432 .1955 8409 15508433 1887 8411 16028434 1929 8412 16118435 1896 8413 15678436 1923 8414 1S528437 1930 8415 i5418438 1949 8416 I1S388439 1935 8417 16138418 1599
8419 lS2S
Avg. 1922 Avg. 1551
78
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TABLE 2D RESULTS OF TIHE LIMIT CYCLE TESTVelocities Corrected to 700r
Rifle SN 789076 (1:14 in. Twist)
175 Meters 253 MetersRd. V Rd. VNo. (ft/sec) No. (ft/sec)8330 2483 103 21288331 2520 105 19978332 2485 106 20328333 2447 107 21418334 2341 108 21038335 2466 109 21338336 2408 110 21828338 2360 111 21288339 2474 112 21858340 2468 113 21168341 2384 114 20178342 2415 8363 21858343 2465 8364 21848344 2490 8365 21838345 2496 8366 21958346 2407 8367 21108347 2490 8368 20948348 2455 8370 20688349 2487 8371 20358350 2417 8372 20808351 2473 8373 20948352 2501 8375 21708473 2455 8376 21708474 2520 8377 21308475 2504 8378 2169847o .2495 8379 22328477 2501 8380 22418478 2470 8382 22518479 2496 8383 21598480 2496 8384 20988481 2485 838S 22408482 2444
Avg. 2462 Avg. 2137
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TABLE 2D RESULTS OF THE LIHMIT CYCLE TESTVelocities Corrected to 700F
Rifle SN 789076 (1:14 in. Twist)(Continued)
339 Meters 450 MetersRd . V Rd. V.No. (f t /sec) No. (ft/sec)
33 1839 8466 147435 1785 8467 149037 1858 8468 141638 1900 8469 144339 1846 8470 15038440" 1840 8471 14608441 19.14 8472 14828442 1817 8494 14508443 1946 8495 15678444 1801 8496 15148445 1857 8497 15488446 1853 "8498 15168447 1883 8499 1491
8448 1784 8500 1550.8449 1830 8501 14326450 1878 8503 14848451 1869 8504 15468452 1795 8505 15258453 1821 8506 15208454 1897 8507 1490,8455 1844 8508 14898456 1787 8509 15478457 1826 8510 15338458 1850 8511 14798459 1835 8512 15068460 1830 8513 15208461 1851 8514 15098463 1851 8515 15968464 1784 8516 15358465 1872 8517 15178518 15598519 1553
Avg. 1845 Avg. 1508
8o
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p.:
TABLE 3 DISPERSION RESULTS
Serial (10 rds) (15 rds). (25 rds)No. mils mils mils125 F
023199 .859 1.223 1.154023294 .981 .779 .88278907o .947 1.345 1.466791707 1.114 1.254 1.205790787 3.067IIall 3.638
700F023199 .847 1.030 1.071023294 1.01 .768 .954789076 1.853 1.652 1.891791707 1.016 1.307 1.203790787 1.942 1.581 1.752O F023199 1.095 .860 1.117
023294 1.110 .980 1.048789076 3.021 .2.599 2.806791707 .867 1.598 1.334
-30 F023199 1.077 1.207 1.233023294 1.187 I.OZ5 1.127789076 2.436 3.832 5.388791707 3.030 3.403 3.396
-650 F023199 1.746 1.074 1.391023294 2.099 1.588 1.810789076 6.833 6.771 6.6.72791707 5.497 6.837 6.567Hall 2.391
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TABLE 3 DISPERSION RESULTS(Continued)
C.I.* C.I.* C.I.*Serial (10 rds) (IS rds) (25 rds)No. in. in. in.
12S F023199 2.04/- .IS 1.18/- .08 1.52/- .11023294 .33/ .70 - .11/ .89 .08/ .81789076 - 2.10/- 2.89 -1.68/- 4.58 - 1.84/- 3.90791707 .24/ 1.00 .56/ 57 .43/ .74790787 1.70/- 1.90Hall .08/- .IS
70 0 F023199 -10.18/ 9.92 -9.87/ 8.96 - 9.99/ 9.32023294 - 5.25/ 7.95 -5.69/ 8.67 - 5.51/ 8.38789076 - .22/- 2.17 .05/- 52 - .06/- 1.18791707 - 9.13/ 6.52 -9.17/ 6.02 - 9.15/ 6.22790787 - 7.00/ 8.64 -6.62/ 9.45 - 6.77/ 9.13
00FF023199 -10.31/ 11.55 -9.54/ 10.62 - 9.85/ 10.99023294 - 3.84/ 8.03 -3.80/ 8.58 - 3.82/ 8.36789076 - 8.49/ 10.47 -7.18/ 9.63 - 7.67/ 9.45791707 - 8.67/ 9.76 -8.81/ 9.85 - 8.75/ 9.81
-30F0023199 - 7.14/ 10.84 -7.14/ 9.87 - 7.14/ 10.26023294 - 8.74/ 7.38 -9.14/ 7.98 - 8.98/ 7.74789076 - 8.41/ 10.38 -9.20/ 8.93 - 8.88/ 9.51791707 - 7.16/ 9.64 -9.46/ 9.47 - 8.54/ 9.54
-65F023199 - 8.92/ 9.12 -9.57/ 8.88 - 9.31/ 8.98023294 -10.49/ .7.77 -9.72/ 7.61 -10.03/ 7.67789076 - .70/ 4.16 -1.38/ 3.40 - 1.11/ 3.70791707 - .16/- .80 3.68/ .74 2.20/ .14ilall 1.87/ 2.58
*Centers of impact at the same range
82
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TABLE S PHYSICAL PROPERTIESNo . IVt. L d cg I x I
inches y(grams) (in.) (in. from b-asel (gm-in 2 ) (gmn-in 2 )Unfired
1 3.549 .745 .224 .303 .0184 .11452 3.529 .742 .224 .300 .0182 .11403 3.540 .746 .224 .303 .0182 .11484 3.538 .748 .224 .301 .0181 .1154S 3.547 .73S .224 .299 .0182 .11476 3.S64 .727 .224 .296 .018s .11517 3.532 .740 .224 .300 .0183 .11398 3.S59 .746 .224 .304 .0185 .11599 3.564 .749 .224 .303 .0185 .1152
10 3.528 .741 .224 .302 .0181 .1145Avg 3.546 .741 .224 .301 .0183 .1148
Recovered1A* 3.532 .745 .224 .303 .0182 .11412A 3.514 .742 .223 .301 .0182 .11303A Not recovcred4A 3.522 .749 .223 .302 .0180 .11525A 3.530 .735 .223 .300 .0181 .11446A 3.564 .727 .224 .296 .0185 .11517A 3.517 .740 .223 .303 .0181 .11338A 3.544 .747 .223 .305 .0181 .11609A 3.546 .750 .223 .303 .0182 .115210A 5.512 .741 .224 .303 .0179 .1139
Av g 3.531 .742 .223 .302 .0181 .114SRecovered
11 3.534 .750 .223 .306 .0182 .116112 3.531 .743 .226 .302 .0183 .117413 3.520 .735 .224 .300 .0182 .112814 3.54S .751 .223 .306 .0180 .118215 3.534 .734 .223 .299 .0182 :11453t.521 .741 .223 .303 .0182 .113917 3.561 .743 .223 .298 .0184 .116218 3.567 .704 .223 .309 .0183 .118619 3.520 .741 .223 .304 .0182 .113220 3.524 .732 .223 .303 .0183 .1133Avg 3.536 .743 .223 .303 .0182 .11S4Avg** 3.534 .742 .223 .303 .0182 .1150* The A's are rounds recovered from the group having th e
same number.**Average for 19 rccovered rounds.85
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UnclassifiedSecurit- Classification
DOCUMENT CONTROL DATA. R 0.(Security claaMilication of title, body of abstrfct and Indefing annotatlomust be enfeiwd when M46overall eport to claslsifed)
1. O0IGIINATIN4 ACTIVITY (Crporate author) 20. REPORT SECURITY CLASSI ICATIONU... Army Aoerdeen Researcn anu Uevelopment Center UcassifiedBallistic Research Laboratories .. j UnclAberdeen Proving Ground, Maryland *,.
3. REPORT TITLE
COIPARISON OF TH E EY2':RIOP. BALLISTICS OF TilE k-193 PROJECTILE IVE.NLAUNCIIED FROM 1:12 IN. AND 1:14 IN. TWIST NI'A1 RIFLES4. OCSCRIPTIVE NOTES (7'ype of rePoUt and Inclusive defes)
S. AU THOR(S) (First name, middle Initial, fasl name)
Maynard J. PiddingtonA. REIPORT CAT& 7a. TOTAL NO. OF PAGES ,?. NO rP REaS
October 1968 92". 7Se. CONTRACT OR GRANT NO. Sa. ORIGINATORS REPORT NU''r9IESl
. ,ROJECTNO. 1T650212D620 Memorandum Report No. 1943.S. OTHER RMEPORNTOI(S (Any ather numbere t Iamy he meelgiedtWe mpOrt)
10. OISTRIUTION STATIEMENTThis document is subject to special export controls and each transmittal to foreigng iernmentsr foreign glatiopals may be made ?nly wito ror val f CQmmanlading.8?,rn .S. Arm AD R i d eeo t gGery S my Berdeen esearc and eve opment Ce ter, eroeen rovng rouM.ary ana. II. SUPPLE.4ENTARY NOTES 112. SPiONSORING MILITARY ACTIVITYI.
U.S. Army :.ateriel Command,S , ,TRCT jWashington, D.C.18). ARISTRACT-, .Thc results of an exterior tallistics test of the 4.193 ball projectilewhen launched from th e t1(-A1 rifle are presented and discussed. Rifles
,SLa twists of 1 turn in 12 inches and 1 turn* in .14 inches were used intie tests. Data were gathered from test firings at th e smallAcerodynamics Range and the Transonic Range of th e Ballistic ResearchLaboratories and from a termporary range set up in th e Climatic Hlanar attile Eglin Air Force IBase, Florida. Tests at ig.lin were conducted at airtemperatures ranging from +125 deg. F' to -65 deg. F.
V!
*1
473I EL S 0FRM11.I AI4.34C ISI"OSIOSEPON ARMY USE. U~a~feD.-.,. --473 " "- '"Unclassified' acuty Clasifi~fcation
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UnclassifiedSecurity Classification14. e O D LINK A LINK KLINK C
MOLe WT JMOLS WT I OLR FIT
Aerodynamic characteristicsM1l6Al rifleSmall armsIM193 projectileTemperature variations
'4
