N AMERICAN RI FLEMAN REPRINT R8 i' It TELESCOPE SIGIITS I 1Ì ',t l!J ;, Ë ü ,i .!t I I { ,L- i f. rd I Characteristics, advantages, disadvantages; checking measuri ng eye relief and exit pupil; correcting parallax; mounts and reticles. Also, selecring and using spotting scoPes and binoculars. .i 'l r, li ,' |t ,l ;t THE AMERICAN RIFLEMAN is the offi- cial iournal of The National Rifle Association ãi Aitt".i"u (NRA). Its readership is well de- a year, $9 for two years, $12.50 for three yeárs. Life MembershiP is $100. For Íurìher in formotion, wrile lhe NRA ot ló00 Rtrode lslond Ave', N'W', Woshinglon 6, D. C. '\*. { 50 CENTS I
measuri ng eye relief and exit pupil; correcting parallax; mounts
and reticles. Also, selecring and using spotting scoPes and binoculars.
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THE AMERICAN RIFLEMAN is the offi-
cial iournal of The National Rifle Associationãi Aitt".i"u (NRA). Its readership is well de-
a year, $9 for two years, $12.50 for threeyeárs. Life MembershiP is $100.
For Íurìher in formotion, wrile lhe NRA otló00 Rtrode lslond Ave', N'W', Woshinglon 6,
D. C.'\*.
{
50 CENTS
I
3rd Printing,
TELESCOPE SIGHTSPaftlof4
By Moi. Gen. J. S. Hotcher, USA (Ret,d)NRA Sroff
A shooter who has used only ironsights usually has an exaggerateâ ideaof what a scope can do fo¡ him. Heknows that a 4-power scope makeseverything look 4 times as large andhe may assume that it will make ã mark4 times as easy to hit. He is in for adisappointment. While the scope doesindeed make aiming easier, it doãs noth-
scope than with iron sights because thescope reduces the normal error of hu_nran vision and shows where the gunis aimed with greater clarity.
Scopes not delicote
conditions. This fear is unfounded. Themodern hunting scope sight in a goodset of mounts is rugged. Telescopesights do have disadvantages, but theseare outweighed by their many benefits.
Advontoges of scopes
Aid to failing eyesight. Shooters ofadvanced age often find it difficult or
Nomenclature of a sight: (a) front mount-ing ring, (c) ,elevat e turret, (e) cover for*i"dur:^I1.9!:,,fÍ) mounr (i) mountingscrew wrth epiece lo oúsing - -- -- -
A comparison of views of a deer as seen with iron sights (l') andwith a 4-Po' er telescoPe
One-power scope on shotgun
average mature hunter does not Possessit in sufficient degree for him to use
iron sights with comfort or confidence.There is no exception to this disappear-ance of accommodation with age; it isinevitable and unavoidable. With thetelescope sight this difficulty disappears,because the objective lens forms itsimage of target or game right on thescope reticle (crosshairs); and when theshooter's eye is focused on the reticle,it is also focused on the target. Many agunner who had thought his shootingdays were over has made a haPPYcomeback by using a scope sight.
Safety. This is highlY imPortant.Many a life has been saved because ahunter who thought he saw a deer, a
bear, or some other animal, has lookedagain through his scope sight whichmagnified the object and showed it tobe not an animal but another hunter.
Easier location of game. The scoPe
serves not only as a sight, but also as
an observation telescope, and can to a
certain extent replace the binocular.The patch of 'snow' on the distant hill-side may turn out to be a mountaingoat or sheep when viewed through thetelescope sight. Through the iron sightsa deer may be either a doe or a buck;with the scope the hunter can instantlytell which it is, and he can better pickhis aiming point on the animal.
Better seeing in poor light. In latetwilight, or early morning before dawn,the scope will often permit aiming wheniron sights would be useless. This length-ens the hunter's daY'
Reduction of cant. ManY huntershave the bad habit of canting the rifle.
The crosshairs of the scope reticle, seen
clearly against the landsoape, make iteasier for the hunter to detect and cor-rect this common error.
Lengthening the point-blank range.The higher position of the scope sightabove the line of the bore, combinedwith the curve of the trajectory, makesit possible to sight the rifle to hit thepoint of aim at a longer distance thanwith iron sights and still have the bulletpass reasonably close to line of aim atall reasonable ranges.
Disodvontoges
lVeight. Putting a scope sight ona rifle adds weight; about 6 ozs. forthe small inexpensive scopes for .22
rimflre rifles to perhaps a pound for a
hunting scope and its mount, and even
more for some of the big target andvarmint scopes.
Added bulk. The rifle with mountedscope is not as neat and streamlinedin appearance as without, and will notgo into a scabbard as êasilY' Also,there is added surface for the wind toact upon.
Change in eYe Position. The scoPe
sits higher on the rifle than iron sights,
and rèquires a stock with a highercomb than that intended for use withiron sights. Either a special high-combstock must be used, or a lace-on orattachable cheekpiece, to bring the
eye where it can be held firmlY in thecenter line of the scoPe.
Rain or snow trouble. A heavY down-pour or a thick wet sno'¡r' can put theicope sight out of action temporarily.
Unsuitability for quick, short-range
shots. The field of view of a scoPe at
short ranges is so small that a chargingbeast closè to the hunter would Perhapsfitl the field of view completely, and itwould be difficult to take aim in a
hurry. If there is a chance of a chargeby a dangerous beast, iron sights
should be relied on'
Scope chorocTerislics
T'here are several inherent features
of a telescope that vitally affect its use
as a gun sight. Some of these will nowbe dãfined-and their effect explained
before we discuss the different kindsof scope sights and how to select one'
Beai in mittd th"te definitions. Theobjective lens, or simply, the objective,is ihe glass lens in the end of the scope
nearest the muzzle' The eYe lens, or
dividuals. If the scope is held at arms
length from the eYe, a bright sPot orcircle of light can be seen on the eye-
lens. This is the exit PuPil.Important characteristics which
affect the performance of the scoPe
are the following:Magnifying Powel. As the PrimarY
functión of a telescope sight is to make
a distant object look closer by makingit appear bigger, magnification is- one
of thè important characteristics of any
scope sight. A scope that makes every-
thing appear 4 times as big, and hgnc.e
onty V+ as far away as it reallY is, is
called a 4-Power or 4X scope.
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3X
The magnification of a telescope sight canbe noted by looking through the scopeat a picket fence with one eye and viewing
the fence with the other, unaided eye
found where these images can be madeto overlap. Then count the number oftunntagnified inrages that cover one ofthe nragnified images as seen throughthe scope. That is the magnification.
Note here a trick which has beenused by mail-order advertisers of cheapnricroscopes and telescopes to makethe purchaser think they are morepowerful than they really are. A 10Xrlicroscope is sometimes advertised asnraking things 100 tintes larger. Thatis because it ntakes everything l0 timesas long, and also l0 times as high. Thearea of the object is then 10 times 10,or 100 tinres greater. That, however,is.
^not the proper way to describe mag-
nification. Properly described, a 4kscope is one that nrakes a l-ft. rulelook 4 ft. long.
Field of view. In looking through anumber of various scope sights it willbe found that there is quite a differenccin the amount of territory which canbe seen, or r'n other words in the anglecovered by the field of view of thescope. Sonte scopes take in a greaterwidth than others. The optical clesignerdescribes this feature in terms of theangle the visible segnrent occupies, butbecause widths at known distaìces areeasier to visualize than the angles, thewidth of the field of view is generallystated in the shooting world as widthof field in feet at 100 yds.
To measure the width of field, placethe scope on a steady rest or stand andaim it at a fence, wall, or the likewhich is exactly 100 yds. distant. Havcan assistant mark the point which is asfär to the left as you can see throughthe scope, and again, without nrovingthe scope or the eye, mark the pointat the extreme right of the field ofview. The distance between these 2marks is the width of field at 100 yds.
If it is difficult to get exactly 100 yds.away, any other distance can be used,rentenrbering that the width of fieldincreases in exact proportion to thedistance. If 50 yds. is used, doubleyour figure to get the correct fieldwidth for 100 yds.
Wide field importontA wide field of view is highly im-
portant for close shooting or for run-ning shots. A 6X scope has a widthof field of only 5 ft. at 25 yds., andit would be hard to get it onto a run-ning deer; but a 2VzX scope has :rfield 12 ft. wide at the same distance.Even for longer range shooting, a widefield is often a great help. The field ofview of a 10X scope is only 24 ft.wide at 200 yds. A wider field nrightsometintes show nearby aninrals otherthan the one being considered for ashot, and these might sometimes bebetter trophies.
Width of field differs sonrewhat withscope construction, but in general itcan be counted on to vary in inverseproportion to the ntagnifying po!¡/er.The 2/zX domestic scopes have widthsof field rnnning fronr 43 to 51 ft., and48 ft. may be consideied normal forthis power. Three-power scopes havea field from 37 to 42 ft.; 4X, from 2gto 35; 5 of the eight 6X scopes ex-anrined have a 20-ft. width of field, 2have 2l ft., and one has 24; 20 ft.rnay be considered normal. Six-powerscopes generally run 15 to 17 ft., andlOX scopes 12 ft. to 14 ft. An approxi-nlation of the nornral width of field ofa hunting scope sight as r.elated tonragnifying power can be had by divid-ing 120 by the power, or if the widthof the field is wanted in degrees, divìd-ing the width in feet at 100 yds. by 5.
It is well to remember that whilethe width in feet gets bigger as the dis-tance increases, the angular width doesnot change. Thus a 4X scope has a30-ft. width at 100 yds., a 60-ft. width'at 200 yds., and a 150-ft. width at 500yds., and so on out; but the angularwidth of the field is 6' at all distances.For a good approximation of the angrr-lar width of ûeld in degrees, clivide 24by the power of the scope.
Variable-power scopes do not haveas wide a field of view for a givenpower setting as scopes lacking thevariable-power feature. Where onepronrinent ntaker's regular 4X scopehas a field of view of 31.5 ft., his vari-able-power scope set at 4X has a fieldof only 26.2 ft., and his regular 8Xscope has a field of 17 ft. as against12.5 ft. for his variable-power scopeset at 8X. In general, whenever a de-sirable feature is added to a scope, ithas to be paid for by a reduction insonre other feature.
There is one exception to the state-nrent that the function of a scope is tonrake an object look bigger. That isthe lX scope which does not magnifyat all but simply shows everything inits natural size. While it does not bringthings closer, it does put the image ofthe object in the plane of the cross-hairs, and hence makes it possible fora shooter whose eyes lack accommoda-tion to shoot well. It has great relativebrightness and a very wide field ofview. Landscape seen through thescope seems to be continuous withthe part outside the scope, the onlycJivision being a thin ring nrarking theedge of the scope field of view. Thecrosshairs just seem to lie out therein space, right on the object at whichthe gLrn is pointed. This feature makesit fast to ainr through, and it is popu-lar with some shotgun shooters.
Besides the IX scope just described,hunting scope sights conte in a varietyof different nragnifications, including2VzX, 23/+X, 3X, 4X, 6X, and 10X.Target ancl varntint scopes conte irrhigher powers, including 12X, 16X,2OX, 25X, ancl 30X. Variable-powerscopes, in which the power ntay bechanged in an instant, are also popularand useful. They come in several com-binations of powers, anlong which maybe nrentioned 21/zX to 4X, 2VzX to8X, 23/qX ro lOX, 3X to gX, 6X to24X, and others. The power is changedby turning the eyepiece housing, or insome cases a separate ring or sleeve.
To check mognificotionChecking the nragnifying power of
a scope is not difficult. Place the scopeon a fixed rest or stand, pointingtowards some suitable object which hasa number of equally spaced objectsplainly visible to the unaided eye, suchas, for exeimple, a picket fence. Thedistance is not important.
Now view the fence or other testobject through the scope with oneeye and directly (not through thescope) with the other eye. One eyewill see the norntal inrage, the otherwill see the enlarged inrage througìrthe scope, and by shifting the headand the scope a bit a position will be
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SHORT EYE RELIEF
The field of view-the diameter at 100yds. of the area seen through the scope-depends on the magnification and- theangnlar size of the pencil of rays enter-ing the eye, which jn turn depends on the
size of the eye lens and the eye relief
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NORMAL
4='--Í330
LARGE EYEPIECE
What can be done bY a maker toincrease fielcl wiitth? We occasionallysee the statenrcnt that a wide field ofview requires a large objective lens,but this is not true. It is only nccessaryto cover Lìp part of the objective to see
that the size of the field of view does
not change. Take a disk of paper thatwilt jLrst cover the whole objective, andcr¡t a snrall hole in the nliddle of it,thcn place the paper disk over theIront surl'acc of the objective. Thebrightness of the image is cut down,br¡t thc size of the field of view re-nrains as beforc.
The attainment of an extra-wide fieldof view requires special eyepiece con-struction which, unfortunately, is ex-pensive. In general, to obtain a wideficld ol' vicw, one must have a big eyc-piccc with large lenses, and a certainbalancc must be sought between thesize of the field of view and the eyerclicf that is considered necessary, forls thc fìcld of vicw gets larger, theeye relief decreases. Thus we have topay for a desirable wide field of viewby acccpting a shorter eye relief,
Eye reliefWhen a shooter looks through a tele-
scopc sight, his eye tt.tust be at theright distancc froltr the ocular lens, orhc cannot see properly. If he movcshis head fronr this position, either to-warcls the scopc or away from it, theeclges of the field of view begin toclosc i¡r ancl finding his target becomesincrcasingly clif'lìcult.
The distance fronr the shooter's eye
to the nearest part of the scope whenthe cye is positioned for best seeing is
callecl the eye relief. As this distancehas an inrportant bearing on the use-l'ulness of the scope, eye rclief is givenin scopc sight specifications.
Optical clesigners trre tattght to thinl<ol' eyc rcliel- as thc distance frorrr thccyc to the surface of the ocular lensjtscll'. But in scopc sights the ocularlcus is usually sct sorlle distance insidethe nretal tube or housing which holcls
it, ancl it beconres uninrportant justlrow f ar it is to the glass stlrface. Whatrlatters is the distance of the eye fron-r
that part of the scope which would firstcontact thc facc in recoil. ScoPemakcls arc likely to report eye reliefas thc distarrcc front the cye to the
lens surface, but in RtnLeveN scoPc
sight evaluation eye relief is alwaysmeasured to the part of the scoPe
which is closest to the shooter's eye,
which after all is the part that flatters.
Determining eye reliefFor high power rifles, the eYe relief
shorrld be at least 21/2" (pteferably 3"if the gun is one with heavy recoil) t<r
avoid having the sight come þack andstrike the shooter on recoil. The rimof the tube can inflict a nasty cut. Thisshoukl be guarded against by holdingthe gun firmly against the shoulder,ancl tensing the muscles to avoid hav-ing the head remain forward as theshoL¡lder is pushed back by recoil. Inadclition, it may be desirable to drawthe eye back front the sight until thefield of view closes in sontewhat; thecentcr of the field together with thecrosshairs or reticle will still be visible,ancl the eye will be at a safer distance.
Making the eye relief long Posesproblcnrs for the scope tnaker. It is
both easier and cheaPer to use a
shorter eye relief when the rifle has
Iittle or no recoil ancl there is no
danger of the scope con.ring back vio-lently and striking the shooter. Accord-ingly, the inexpensive qtrick-rnountingscope sights for .22 rinrfire rifles areusually made with an eye relief of 2"or less, which is entirely satisfactory.
In catalog descriPtions of scoPe
sights we often see eye relief statedin tern.rs such as 3" to 5", thus implyinga considerable and very desirable de-grec of latitude in permissible eye posi-tion. Unfortunately, scope sights do notpossess any sttch degree of flexibility incye relief. The proper eye position is
that from which the entire fleld of viewcan be seen clearly frotrl edge to edge.
ln general, if the eye is nroved morethan about t/2" ãway from this opti-r.rrum position, either toward the eyelens or away fronr it, thcre will be a
nrarked reclttction in the fielcl of view.A lcacling rlaker of optical instrtlnrentshas st¿itecl: "Laboratory llleasLlrementsl'eveal that no rifle scope offered onthe nrarket provides a usable range ofeyc position âs greât as one inch, withinwhich 95o/a of the full fielcl of view canbe secn."'tFocts olrout Telc,scopic Sighls, Buusch a I'otttbOptí<al (tt
It is true that if the eYe is movedback several inches, a small hole canstill be seen through the scope, but suchviewing is very unsatisfactory as com-pared to what is seen when the eYe
is properly placed. There is little dif-ference between the various makes ofscope in this matter of latitude of eyeposition, as it depends largely on thediameter of the entrance pupil of thetuser's eye, which is beyond the controlof the scope deslgner.
We have experimented with manYdifferent scope sights in all usual powerswith a special fixture in which the scopecan be nroved backward and forwardand the distance to the scope from theeye read on a graduated scale. A typicalresult with a 4X scope sight of excellentdesign gave the optimunt eye point as
33/q" . When the scope was nroved closerto the eye, it was noted that the edges
of the field were starting to close in atan eye distance of 3Y+", and at 3" thefield was reduced to about one-half itsoriginal area unobstructed. When thescope was moved away from the eYe,
the field started to close at 4Vt" eyedistance, and at 5" there was only aboutone half the original area 19ft unob-strr¡cted, though it was still possibleto aim with the reduced field of view.
Core in mountingIn rrounting a scope on a rifle, care
lnust be used to position it to suit theuser. By loosening the clamp rings whichhold the scope tube in its nrottnt, thescope cân be slid backwards and for-wards. First loosen the ring screws,then have the shooter hold the rifle inhis normal shooting position and lookthrough the scope while it is shiftedbackwards or forwards to suit him.Then tighten the clantp ring screws.
Occasionally, it will be found thatbecause of interference between therange and windage adjustment turretor sonre other part of the scoPe andthe rings of the mount, the scope can-not be moved far enough one wâY or'
the other to suit sotre shooters. Thiscliflìculty can sontetimes be overcomeby the purchase of offset nlountingrings, which perrrrit the scope to bepositionecl farther forward or back, ac-cording to the way the rings are turnedwhen putting thenr on the scoPe. I
(1., below) Checking eye relief of a telescope sight with specialmôasuring clcvice. ihó slider holtling the scope hits tt. spt'ingplunger õperatccl by a level trndel'neath. Scope ancl slicler aleslicl ¿rlonc-bar t¡ntii optimttnr ficlcl of view is obtainecl. Lever
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is then t'eleasecl, locking scope in position trntil-ey-e- r'eljef .canbe reacl off the ócale. (r'- Uelów) Chtcking eye lelief by lookingihrough the scope while it is mountecl on a rifle in actual
shooting Position
TELESCOPE SIGHTS
^ NYoNE shopping for a telescopic
fl sight will notice at once that thereis a marked difference in the size of thefront end of the scope tube among thedifferent scope sights found on the.market. This is due to differences in thesize of the objective lens at the frontend of the telescope which first gathersin the light rays and brings them to afocus inside the scope tube.
Most inexpensive, quick-attachablescopes for rimfire rifles have rathersmall objective lenses, in the order of/2" or 7a" diameter. Hunting scopeshave objectives running from about Zs "diameter (in a l" tube) up to nearly 2"diameter. A normal 4X scope may havea bell-shaped front end holding an ob-jective lens about 1Y+" wide. Targetscopes are found with objective lensesof 1", l/a", 7Y2", and 2" diameter, atprogressively higher prices for eachlarger size. For example, in one well-known and high-grade make, a scopewith a lV+" objective sells for one-thirdmore than the same scope with l'objective; the 11/2" objective scope sellsfor 56Vo more, and the 2" objectivescope sells for over twice as much as thel " scope.
Logical questions are: Why are thetedifferent objective sizes? What are theadvantages and disadvantages of largeobjectives? What factors determinechoice of objective size?
Telescope users in general have longbeen accustomed to think of the per-formance of telescopes, especially largeastronomical telescopes, in terms of ob-jective size. So fundamental is this thatit has become the practice to describe
PaftZ ol 4By Moi. Gen. J. S. Hotcher, USA (Ret'd)
NRA Stoff
such telescopes in terms of objectivesize, as for example the 40" Yerkesrefracting telescope and the 2OO" re-flector at Mt. Palomar.
For reasons connected with thetheory of optics and the wave length oflight, the resolving power of a tele-scope of high magnification is limitedby the objective diameter. Thus for as-tronomical telescopes, where the per-formance depends on the highest pos-sible resolving power, it becomes of thevery greatest importance to have thelargest practicable objective, or, as theoptical people say, the largest aperture.However, the magnification used in tele-scopic sights is relatively so small thatthis consideration does not enter, andthe size of the objective is determinedon the basis of the light-gathering abilityconsidered necessary, together with aconsideration of the undesirable bulki-ness of a scope sight with a very largeobjective.
Foclors musl be boloncedIf the objective of a scope sight is
made too small for the power of thescope, it will not gather enough light.and the scope will not do well on darkdays, in the late evening, or early morn-ing bours. On the other hand, a largeobjective makes a costly, bulky scope,unhandy to mount. These factors mustbe balanced to fit all circumstances inan optimum manner.
Objective size is very closely tied inwith the size of the bundle of rayscoming out of the eyepiece, called theexit pupil.
The objective lens of a huntingscope sight should have a diameter inmillimeters of not less than the magnify-ing power of the scope multiplied by 5,witb 6 times the magnifying power as a
probable optimum. Thus a 4X scopewould need an objective of at least 20mm. diameter, a 6X scope a 30 mm.objective or larger, and an 8X scope a40 to 50 mm. objective.
But here another consideration enters.The front outside diameter of a scopewith a 40 mm. objective would be about1-15/16", which would generally be ashade too large to mount in the usualmounts and might require extra highmounts in some makes. Confrontedwith tbese facts, the purchaser mightprefer a 6X scope which would com-pensate for its slightly lower magnifying
power by being of a handier size.The bundle of rays coming out of
the eyepiece of a telescope convergesand all rays pass through a small cir-cular area outside the scope and behindthe eye lens, called the Ramsden circle,or exit pupil. It is the image which theeye lens forms of the aperture of theobjective lens, and is located at the eye-point, where the eye of the observermust be placed to obtain the largestfield of view and the greatest brightnessover that field. Exit pupil size is usedas a measure of the amount of illumi-nation of the instrument. With anygiven magnifying power, the larger theobjective lens. the more light gatheredand the larger the exit pupil will be.With any given size objective lens, thegreater the magnifying power, thesmaller the exit pupil. A rule to re-member is that the diameter of the exitpupil is equal to the unobstructed di-ameter of the objective lens divided bythe magnifying power of the telescope.If the apparent aperture of the objec-tive is reduced by internal stops, as isoften the case in cheaper telescopes,the exit pupil will be reduced in size.
Meosuring eye reliefBecause the exit pupil is located pre-
cisely at the point where the eye mustbe to obtain the optimum field of view,the distance from the scope to the lo-cation of the exit pupil is the same as
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Objective lenses vary greatly in sizesharply focused on ground glass, then
eye relief is read off the scale
the eye relief, which gives an excellentmethod of nteasuring eye relief withgreat precision. Place the scope in a
trough mounted on a tripod and point-ecl at the sky. Across the rear end ofthe trough place a piece of groundglass, and then nrove the scope until thebright spot thrown by the scope is insharp focus. The distance to the scopeas measured by a scale laid in thetrough is the eye relief.
In using this method it will be foundthat there are 2 different points at whicha sharply defined round spot of lightwill be thrown on the glass. One isthe true exit pupil, which is the imageof the objective; the other is the imageof the erecting lens system, and usingthis for the eye relief will give an in-çorrect result.
TUB RrRlew¡N has devised a nreth-od of guarding against this error. Cutout a disk of paper the size of theobjective lens, and then form an open-ing of distinctive shape such, for exam-ple, as a star in the center of thepaper. Placing this paper disk againstthe front surface of the objective lens,proceed as before, but with no risk ofusing the wrong spot of light, becausethe exit pupil now has the easily recog-nized shape of the disk opening, whilethe false exit pupil formed by the imageof the erecting lens remains round as
before.
lmportonce of exit pupil size
The area of the exit pupil of a tele-scopic sight as compared to that of theuser's eye pupil is a measure of theability of the scope to perfornr underpoor Iight conditions.
To compare this ability of telescopesor binoculars to perform under adverselight conditions, the optical people usea ternl called relative brightness, whichis defined as the algebraic square of thediameter of the exit pupil in nrillime-ters. If a scope has an exit pupil of 3
nlnr. in dianreter, then its relativebrightness is 9.
As the size of the exit pupil variesdirectly as the size of the objective lensfor any given magnifying power, it willbe seen that large objective size givesa scope sight its ability to perform inpoor Iight.
In deciding on how large an exitpupil we would like, we must considerthe fact that the eye of the telescopeuser beconres an integral part of theoptical system. It is true that the largerthe objective lens, the nrore Iight thescope will gather, and the greater therelative brightness figure that can bequoted. Realize, also, that an exit pupilthat just nratches in size the pupil of theuser's eye will give him all the light hecan utilize, and that part of the exitpupil which falls outside the pupil of
the user's eye simply is wasted.Exhaustive studies have been made
to find out just how large the humanpupil is under various conditions oflight intensity, and these studies arepublished in standard works on optics.It has been found that the pupil of thehunran eye has a dianreter of about 3
mnr. under conditions of bright sun-light, and that it autonratically getslarger as the light gets dimrner until itreaches a diameter of 5 mnr. to 6 mnt.in deep twilight, and 7 nrnr. in com-plete darkness. As a practical matter,any scope with an exit pupil of 3 mm.or over gives a good bright inrage infull sunlight. But if the exit pupil is nolarger than 3 mm., the glass will beginto fail and everythi¡g will get difficultto see when the sky becomes heavilyovercâst or twilight deepens. On theother hand, ¿Ì scope with an exit pupilof 5 rlnr. or 6 mm. diameter will con-tinue to show objects in deep twilighteven after they are difficult to recognizewith the unaided eye, and long afteriron sights have become useless.
We often see it written that the in-ability of the htrnran eye to accept a
bundle of rays nrore than about 5 nrnr.in diameter makes it useless for theexit pupil of a scope to be larger thanthis nrinimum desirable size. Othertinres we will see it written that a muchlarger exit pupil is desirable'because itlequires a less critical placenrent of theuser's eye-that is, that the user cansee through the scope without placinghis eye exactly in the center line. Butif the eye is not in the optical axis,any parallax which nray exist and wocrldotherwise not be noticed will beconrevisible. This of course is ttndesirable,and tends to oftset the advantage ofgreater ease in finding the proper eyeposition. Of course the rifle should beproperly stocked so that the eye willnaturally Iine up with the centcr line ofthe sight, but this condition does not al-ways exist, and a very large exit pupilwill permit the eye to be placed consid-erably out of line with possible increasein visible parallax.
All things considered, it seems thatan exit pupil of about 6 mnr. diametershould be a satisfactory conrpromise.This ties in with the question of whatis the most desirable objective size, as
has been seen in the previous section,so that the desire for an extra largeexit pupil must be balanced against theext¡a cost and bulk of an over-sizedobjective.
Reticles
To pernrit the scope sight to belined up accurately on target or ganle,theré nrust be visible in the field of viewa fixed reference point, such as cross-hairs, an ainring post with or withouta horizontal crosswire, a dot, or thelike, which is used as an ainring point.This is called the reticle (or reticule)lronr the Latin reticulanr, diminutiveof rele, a net.
Crosshairs for scopes are nrade invarious widths, or thicknesses, of wire,spider web, or etched lines on glass.The sanre actual width of crosshair willlook thicker with a high-power scopethan with a lower power. This effect isquite apparent with a variable-powerscope, in which the hairs seem to be-come thicker as the power is increased.In spite of looking thicker at higherpowers, the same hair will always sub-tend the same angle, and will cover thesanre amount of space at 100 yds. at3X as at 10X, though in the latter'case it Iooks over 3 times as thick.That is because the other objects seenthrough the scope increase in the santeproportion. If the crosshair covers aninch at 100 yds. at 3X, that sante inchwill look like 31/t" at the lOX settingof the scope and the magnified cross-hair will still just cover it.
Crosshairs are sometimes simply veryfine lines etched on a glass plate. Thishas the disadvantage that, as the eye-piece must be sharply focused on thereticle, any small particles of dust,fungus, or any other foreign object onthe glass reticle plate will show upsharply in focus and be magnified.Moreover, the glass plate adds 2 more
7
Pupil of eye5 mm.
Exit pupil of scope mm.... ALL USED
Pupil of eye5 mm.
Lorger exit pupil . . . ONLY 5 mm.USED
An exit pupil larger than 5 mm. cannot be fully utilized by the eye, since only in dark-ness does the pupil of the eye open up larger than 5 mm.
Several types of reticles used in telescope sights: (1.-r.) vertical post and interruptedcrosshairs, crosshairs, crosshairs with dot, and taþered post and horizontal crosshair
surfaces from which partial light re-flection can occur. However, a glass
reticle is used to advantage both in a
ZlzX ¡o 8X variable-power huntingscope and in a 6X to 24X variable-power target scope. The lines of thereticle are made fine in the middle, andtaper to a greater thickness at the ends.As magnification is increased, the linesare magnified, but at the same time thefield of view gets smaller, so that thethick ends of the lines are no longerseen, which gives an illusion of cross-hairs that remain the sante thickness as
the power is increased, As to the mostdesirable size or thickness of crosshairs,it may be said that very thick ones aresometimes too coarse to define the aim-ing point well and may seem to coverup too much of the animal or target,while those that are very fine are diffi-cult to see in poor light or against abrushy background.
If in doubt between 2 thicknesses ofcrosshair, choose the thicker. Cross-hairs that are too fine will cause ascope to wash out and become uselesswhen the light becomes dim, as in deeptwilight. Crosshairs that are very thingive a fine precise aiming point in goodlight and with favorable backgrounds,but are too hard to see under adverseconditions. It is better to have a cross-hair that is easy to see against a dark,brushy background.
Dots and posts. While the plain cross-hair is the most universally popularreticle for scope sights, and is the bestfor target scopes, other types which havetheir usefulness for hunting scope sightsare the dot and the crosshair withainring post. The dot is a snrall sphereof plastic suspended in the center of thefield of view by means of verticaland horizontal strands, the dot beingformed at the point where thehairs cross. The web of the blackwidow spider is used, and thisweb conres out of the abdomen ofthe spider in 4 strands which then com-bine and stick together to fornt the fila-ment which is tough, elastic, and strong.For use in supporting the dot, the fila-ntent is separated into its 4 individualstrands, each of which is rolled up on a
separate reel, so that the strand actuallyused to support the dot is only Za asthick as the usual spider web. Thisgives the illusion that the dot is simplyhanging in space with no noticeablesupport. Dots rnay be had in definitesizes, to subtend certain angles or covercertain widths at stated distances. Adot of known size may therefore aid inrange estimation. For example, a 3-minute dot will cover 3" at 100 yds.,and if it seems to cover about 6" ona deer, then the shooter may safely as-sunre that the deer is about 200 yds.away from him.
Crosshoirs or dotThe choice between crosshairs and
dot is one of individual preference, andfor the shooter who has never usedeither kind plain crosshairs would prob-ably be the safer choice. If a dot iswanted Iater on, the scope maker caninstall one at a small charge.
A flat-top tapered post with horizon-tal crosshair is another type of reticlethat is highly useful in certain cases.
With a good scope sight, it is possibleto shoot long after iron sights haveceased to be visible in the twilight, orbefore they can be seen in the earlynrorning. But often in very poor light,especially in the woods, ganle can beseen perfectly well in a scope and thecrosshairs can be seen only with dif-ficulty or not at all. In such cases, theflat-top post can be plainly seen, and ishighly useful, though for long-rangehunting in good light it is not as desir-able as plain crosshairs because the postoften hides enough of the ganre animalto nrake it an annoyance, and besidesit is harder to 'hold over' for a longshot with a post than with crosshairs.
Like the crosshairs or dot, the postcan be had in definite minute widths oftop to help in range estimation.
A type of reticle which has becomepopular in Europe for hunting rifleshas a heavy horizontal line. interruptedfor about 1/+ of its length in the middleof the fietd, plus a vertical post witha pointed top. Such reticles are oftenseen in scopes nrounted on importetJhunting rifles.
So one can correct his aim whennecessary, sonle arrangement must beprovided to permit vertical and hori-zontal movenrent of the point of ainr-crosshairs, top of the post, or the dot-to give range and windage changes.
Such adjustments may be effectedeither by moving the reticle in the scopetube (called internal adjustments) orby having the reticle fixed in the scopetube and moving the entire scope in itsnrount (called external adjustments).
Internal adjustments havr: the ad-vantage of simplifying the mount, whileexternal adjustments have the impor-tant advantages of greatly simplifyingthe scope construction, making it easierto waterproof, keeping the crosshairs al-ways in the center of the field of view,and eliminating a frequent cause oferror, which is the tendency of the cross-hairs to fail to follow changes of wind-age and elevation knobs.
With scopes having internal adjust-nrents, there is a knob on top of thescope tube for making elevationchanges, and one on the side for makingwindage changes. These are in the formof little turrets, usually covered withscrew-on caps to keep out moisture.Turning the elevation knob raises orlowers the crosshairs, while the windageknob moves them from side to side.Most elevation and windage knobs havescrewdrive¡ slots often made wideenough so that a coin nray be usedto turn them, and many also have ser-rated edges so they may be turned bythe fingers alone. Some have clicksso that the user nlay keep track of theamount he turns the knob, while othersdo not have clicks but are graduatedaround the rinl so the anrount ofchange can be determined visually.In low-powered scopes, each click ordivision is usually 7z nrinute, corre-sponding to a Vz" movement of the
Elevation and windage knobs on htrntingscope sight with internal adjustments
2.¡t*rtI=
dr I
>
I
group at 100 yds. Higher Poweredscopes such as 8X and lOX are likelYto have Y+-minute clicks or graduations'
In buying a hunting scope, be surethe windage and elevation knobs arenrarked to show which way the shotwill be nroved when the knob is turned.There is a lack of uniformity amongnlanufacturers on this matter, and unlessthe adjustments are marked confusionand waste of ammunition will resultwhen sighting-in.
With many scope sights, the cross-hairs seenr to move out of the centerof the field of view if large changes ofelevation or windage are nrade and theoff-center appearance of the crosshairscan be disturbing. This effect is avoid-ed in several of the better scopes by theuse of a design in which, when changesare made, the crosshairs do not seenrto nrove in relation to the circular fieldwhich is seen by the eye but remaincentered at all times. If the rifle withsuch a scope on it is placed in a fixedrest and the windage or elevation screwsaie nroved, the target will seem to moveacross the field of view while the cross-hairs seem to stand still. This is a de-sirable feature.
PorolloxWhen focusing a scope sight the
eyepiece is screwed in or out until thereticle or crosshairs are sharply in focus.If the objective lens has been correctlyplaced, it will project the image of anyobject at nornral hunting range so thatthe inrage lies precisely in the plane ofthe reticle, and the inrage also will beseen in sharp focus. Moreover, as theeye is shifted side to side or up ancl
down there will be no apparent nrotionof the reticle in relation to the target.
However, if the objective does notproject the image into the sanre planeas that occupied by the reticle, therewill be an apparent relative nrotion be-tween target and rcticle. With this con-dition there will be sonre uncertainty as
to just where the bullet will hit on thetarget. It nray be at any one of theplaces that the intersection of the cross-hairs seenrs to rest as the eye is shifted.Obviously this interferes with very ac-curate shooting. This effect is calledparallax.
Dislqnce of subiect from scope
The closer an object to the objectivelens, the farther back from the lens theinrage is formed. There is quite a bigdifference in distance front the lens ofirrages of an object 50 ft. in front of itand one 100 ft. away, but much lessdifference between the images of an ob-ject 50 yds. away and one 100 yds.away; and after a distance of 100 to200 yds., there is little separation be-tween images of objects from this pointon out to infinity.
The maker of a scope sight can pickany one range and so position the ob-jective lens that there will be no parallaxat all for that range, but there wilt be atleast sonre small degree of parallaxpresent for all other ranges. However,if the objective lens is set so that theinrage of an object '150 yds. away isfocused exactly on the crosshairs, theparallax for all objects more than 100yds. away will be so small as not to beat all bothersonre. When objects closerthan 100 yds. away are viewed, someparallax will be noticeable, and thecloser the object, the greater ¡t will be.Moreover the object will be out offocus, and not sharp.
For this reason, it is never a goodthing to test a hunting scope inside a
sporting goods store. Objects seen willbe too close for either a sharply focusedinrage or absence of parallax. The scopeshould be taken to a good vantagepoint ancì judged by observing objects¡.rt least 100 yds. distant.
It should be noted that with scoPes
of higher magnifying power, parallaxis nrtrch nrore noticeable than it is withlower powers, and with scopes ofaround lOX it may become a problem.For this reason 8X and 10X huntingscopes often have movable objectives,which can be adjusted by the owner toelinrinate parallax at the range mostusually encountered.
High-powered target scope sights ofI 5X to 30X are invariably arranged so
the objective may easily be screwed inor out to eliminate parallax for theexact range being used, and the rangesetting is marked in yards near the rimof the objective. However, sonte high-powered (8X, 10X, 12X) varmintscopes are made without this parallaxadjustnrent, being constrttcted to havenrininrum parallax at average varmintranges of I 50 yds.
Variable-power hunting siopes withpowers up to lOX will usually showsome parallax at the higher power set-tings, but this nray generally be disre-garded because the cheek of the shoot-er, resting against the conrb of thestock, will hold the shooter's eye innearly a constant position with regardto the center line of the scope, and ifthe eye does not nrovg there can be noparallax.
The anrount of parallax depends onthe distance of the primary image fromthe reticle and on the amount the eyeis permitted to move. There can be noparallax at all if the primary inrage isin the plane of the reticle, or the eye ishetd in a fixed position and does notmove out of the center line of the sight.
Correction of porolloxA consideration of the preceding
gives us the following rules for the cor-rection of parallax in scope sights:
First focus the eyepiece on the cross-hairs by pointing the scope at the skyand screwing the eyepiece in or outuntil the reticle is as sharply defined aspossible. (For nrininum eyestrain, it isbest to start with the eyepiece screwedto the rear, then screw it forward untilthe reticle gets sharp.) Check this ad-justnrent by looking away into the fardistance for a few seconds, then quicklylook back into the scope. The reticleshould still be sharp; if it is not, re-adjust it until this can be done.
Now place the scope on a firnr standor rest, pointing at â target at the rangeat which the scope is nrost likely to be
Fl
t
Parallax occt¡rs when the objective lens does not project the image to the same planeas that occupied by the leticle
9
used, and check the scope for parallax.If the scope is a target scope, or a
high-powered hunting scope with mov-able objective, then move the objectiveforward away from the reticle if theimage of the target as seen in the scopemoves against the motion of the eye,or move the objective lens towards thereticle if the image of the target seenin the scope moves with the eye. (Withmost high-powered target scopes thiscan be done simply by setting the ob-jective to the marked range positionson the body of the scope near theobjective - adjusting arrangement. Withsuch scopes the objective itself does notturn when this adjustment is ntade, butsimply slides straight forward, whichavoids any chance of changing the op-tical axis, as might happen if the ob-jective had to be turned.)
Correcting hunting scopes
In an ordinary hunting scope with noprovision for movement of the objec-tive, the only way to correct parallaxis to shift the reticle into the plane ofthe image fornred by the objective. Thereticle on internal-adjustment scopesights is carried by the turrets holdingthe range and windage adjusting screws.If the image of the target as seen in thescope has motion relative to the reticle,and seems to move in the sanre direc-tion as the shooter's eye, then the imageis forward of the reticle and the reticlemust be shifted forward to correct theparallax. To shift the reticle, loosen thescrews holding the range and windageadjustment turrets, but do not take thescrews all the way out (this may castadrift the reticle holder) and do notlift the turrets up off the surface of thescope tube (this will break the water-proof seal). With a sharp-pointed pen-cil mark the exact position of the turreton the scope tube; then, holding a
blockofwood against the turret, gentlytap it in the clesired direction, re-focus-ing the eyepiece on the reticle eachtime it is moved and checking by look-ing through the scope until the parallaxis eliminated.
If all the parallax is eliminated at arange of 150 yds., there will be littleparallax noticed at any normal hunt-ing range with comparatively low-pow-ered hunting scopes.
In some scopes movement of theturret, as described above, is not possi-ble as the.turret may be made integralwith the scope tube. In these scopesthe reticle is held in a tube which slidesinside the main scope tube, and is keptin place by screws near the turret whichlock the reticle holder and preventit from sliding. If such a scope needsparallax correction or adjustment, theowner should have this work done atthe factory. I
Scope Síghts lo, Old RíflesN í ANy interested in firing old rifleslVl and muskets find that thecrude sights make precise shootingdifficult. I have a system of mount-ing scopes on several types of oldrifles which does not involve altera-tion of the gun. I mount adapterplates on the guns using existingscrew holes. Depending on theirlength and function, original screwsmay be used, but in some caseslonger screws must be made. A com-mercial scope mount for flat receiv-ers is then mounted on the adapterplate.
A requirement is that the rifle havea sizable flat side with at least 2large, widely spaced screws. Typi-cal arms meeting this requirementare the Civil War rifles and rifle-muskets, the trap-door Springfields,and the Remington rolling-blocks;also some of the lever-action repeat-ing rifles. For the trap-door Spring-fields, the mount nlust be reversed tooffset the scope to the left so thatthe action can be opened.
I make the adapter plates of hard75-ST aluminum (3 I 16' thick isabout right). The Weaver N-5mount is mounted oñ the plate with8-32 screws and nuts. Thê rearholes are elongated for vertical ad-justment and shims between mountand plate give horizontal adjustment.
With the rifle-muskets and trap-door Springfields'the regular lockscrews are used. The heads may becountersunk into the plate. Screwsshould be drawn up tight but ex-treme force should not be used so asto avoid crushing the stock. Withthe Remington rolling-blocks, theguard plate screws are replaced withlonger screws. The bottom screwmay be countersunk into the plate.The action pin holes are beveledfrom the back to clear the pin heads.Back of the plate is recessed to clearthe extractor screw head. All largemilitary rolling-blocks have identicalscrew spacing, so one plate will fit allrifles.
Several scopes with t/c" tubes areavailable and split bushings can beused to adapt /a" tube scopes to theN-5 mount. Do not use scopesmade for .22 rifles as their eye reliefis too short.
This method of mounting gives arather high scope and a lace-oncheekpiece is helpful.
Many old rifles will give unexpect-ed accuracy with a scope. Several ofmy Remington rolling-blocks aver-age under 2" at IOO yds., with oc-casional groups as small as 1
/.-M¡RrrN E. A¡-csn
$ezxrer. ÀT-5-ðÁ,cvnt
Ptale
(Above) Adapter plate mounted onmuzzleloading cal. .69 Plymouth Navyrifle. (Below) Adapter plate completewith mount and scope mounted on 8
mm. Remington rol,ling-block rifle
Iaa
Ca
l0
TELESCOPE SIGHTS
/-f\HE telescopic sight must have some
I means of holding it onto the rifleand of aligning it parallel to the bore.Hunting scopes have one system ofmounts, and target scopes an entirelydifferent system, while the inexpensivescope sights intended for rimfire cal..22 rifles have a simplified type of sightmount different from either of theothers.
Hunting sight mounts. The tYPicalAmerican hunting scope sight is nor-mally held in its mount by rings whichencircle the tube and can be drawnup to a tight fit by clamping screws.There are 2 main varieties of mountrings: the solid rings which are slippedonto the tube of the scope from theends, and the hinged or split type whichcan be opened up enough to be fittedonto the tube without going over theends. The so-called solid type usuallyhave a split at the top or on one sidewhich permits the ring to spring apartenough for it to slide easily, and whichpermits it to be drawn together tightlyby the clamping screw.
Rings are made in various sizes to fitthe many different sizes of scope tubewhich can be found on the market to-day. Lately the tendency has been forAmerican scope sight manufacturers touse a l" outside diameter for the maintube of the scope, but many other sizeswill be found, especially among the im-ported scopes.
Solid mount rings are simpler andneater in appearance, but have the im-portant disadvantage of requiring theeyepiece to be unscrewed from theBcope so they can be slipped overtbe end of the scope, Also, the adjust-ment turret may have to be removed topermit the front ring to slide forward toits proper position, unless the objectivelens is small and the front end of thetube is of the same diameter as themain portion. Many scope sights havean enlarged portion or 'bell' to housethe objective lens. Sometimes this partthough appearing to be solid with thetube, can be unscrewed and removed topermit the front ring to be slipped ontothe tube. As removing either the eye-piece, turret, or objective cell breaksthe moisture-resistant seal provided atthe factory, this should be avoided ifat all possible. For this reason splitrings are recommended, as they can be
opened up and placed on the tube atany desired spot.
Part 3 of. 4By Moi. Gen. J. S. Hotcher, USA (Rel'd)
NRA Sroft
With the rings on the scoPe tube,there must be a means of attachingthem to the rifle itself, and this is doneby means of a sight base or bases onreceiver or barrel. Often there are 2
bases, one on the front ring of the re-
A hunting scope sight mounted with attachable mount base and split rings
Hunting scope mounted in flexible steel band split rings
Split rings are convenient to apply scope mount with standard split rings
Target sight bases on high power rifle
ceiver and the other on the rear ring orreceiver bridge. A popular sight base
is the bridge type, which straddles thereceiver opening in bolt-action rifles,being fastened with 2 screws in the re-ceiver front ring and one or 2 mote
ll
screws in the rear ring of the receiver.Bases of this type are made in many
slightly differing designs by a nunrberof scope-sight makers and by somenrakers of mounts who do not produce ascope sight of their own. A more orless standardized spacing for the screwswhich attach bases to the receiver hascome into use, and ntost sporting riflesof recent manufacture have tappedscrew holes in both the front and rearreceiver rings to permit easy attachmentof sight bases. The holes have fillerscrews when they come from the fac-tory, and it is necessary for the gunowner who purchases a sight mountonly to remove these screws and at-tach the mount with the screws thatcome with it.
While this makes it easy for the own-er to mount his own scope, in someother ways it is not ideal. For example,the recoil of a high power rifle subjectsthe sight mounts to a considerablestress, and the screws may loosen a bitin time, especially if they happen notto have been turned up tightly in thebeginning. Some imported hunting riflesemploy a system which is sounder froman engineering point of view-tbe basefor the scope sight is made integral withthe receiver rings.
Sights with roilsThe Germans, who are old hands in
the design and use of telescope sightsfor hunting rifles, have a clever andsimple method of holding a huntingsight on the rifle without the use ofrings. Along the bottom of the scopetube there is a rail of dovetail cross-section, and the rifle carries a track orrib into which the rail on the sight willslide, to be tightened in place by clampscrews. This avoids all trouble withmounting rings, such as interference be-tween the rings and the turret, whichoften occurs even with hinged or splitrings when an attempt is made to slidethe scope forward or backward in therings to adjust the scope to the propereye relief.
European scope sight with integral mount-ing rails shown with a side mount which
can be fitted to many hunting rifles
12
åti-J
European rifle with integral sight bases:(a) Scope mount which fits these integralbases and (b) iron peep sight which attachesto rear base when scope sight is not used
This simple and eftective method ofmounting a scope sight is hardly seenin the U. S., except in the case of afew imported hunting rifles which havethe sight with rail and the base to fit.Such scopes are imported and sold, andcan therefore be had if desired, andsight bases which will fit them can behad from some domestic makers.
Most mount bases which are held onby screws depend on the accurate loca-tion of the screw holes to line up thescope approximately with the gun boreafter which final zeroing is done bymoving the reticle with the elevationand windage adjustment screws. How-ever, some mount bases incorporateindependent adjustments for correctingboth elevation and azimuth. Occasion-ally, when the scope is found to be toofar out of line, one must resort tochanging the position of the bases byshimming.
In some of the older types of bolt-action rifles, such as the 1903 Spring-field and the military model Mausers,the bolt handle and the safety lock in-terfere with a l,ow-mounted scope, andit is necessary to have a gunsmith alterthe bolt handle and install a differenttype of safety lock.
Modern bolt-action sporting rifles allhave these points taken care of so thatscopes can be mounted on them suc-cessfully without interference from thebolt handle or safety.
In lever-action rifles, such as theWinchester Model 94, which eject theempty shells upward, it is not possibleto attach the sight base directly on topof the receiver, The base must beplaced on one side and the scope tubemust be offset to the left or else ashell deflector must be used to guidethe empties out to the right and preventthem from falling back into the open-ing and causing a jam.
Detochoble mounts
Most modern hunting scope mountsare so made that the scope and its ringscan quickly be taken off the rifle with-out disturbing the zero. This is desir-able because the scope is less liable todamage in transportation if it is notmounted on the rifle. In some types ofmount, the scope and its rings are ar-
Lo-Swing scope mount in shooting posi-tion. Mount is hinged so it can be swungaside to permit use of iron sights in an
emergency. It is also quick detachable
Lo-Swing mount swung aside to permituse of iron sights
Lo-Swing mount with scope detached.This is done by turning the serrated
cylindrical nut
ranged to slide onto the base or bases,and are locked in place by levers, ordisk screws with serrated edges to betightened by the fingers, and usuallywith a coin slot also, to permit a cointo be used as a screwdriver to tightenthe mounts more firmly on the bases.These screws should be turned up fairlytight, but care should be taken not touse excessive force, and to tighten thescrews to as nearly as possible the samedegree each time, A variation in thetightness may show up in a change ofzero of the scope.
Several makers of scope sights pro-vide for the attachment of a small peepon the rear mount base for use whenthe scope is removed. There are severalexcellent scope mounts on the marketthat are hinged so that the entire scopecan instantly be swung over to the leftout of the line of sight to permit thefast use of iron sights in ahy emergencywhere the scope may not be suitable.
Hunting scope without range or windage adjttstments, for use where adjustments are
in the mount
--Él'r'1tçt
Hunting scope mount with elevation and windage in mount
necessary the provision of long eye re-lief, which is exPensive.
We find, therefore, a whole class ofefficient but very inexpensive scopes
which are suitable for plinking riflesand for .22's which are used for smallgame or Pests.
These little scoPes, usuallY of 4X,formerly used mounts which were at-
tached to the side of the rifle bY
several screws. While these mounts are
still available, they have been largelysuperseded, at least for newly producedrifles, by a system which both the rifle-nrakers and the scope manufacturershave adopted, of grooving the receiverof the rifle and Providing a mountwhich will slip instantly into thesegrooves, to be tightened in, place byicrews. Such mounts, originally intro-duced under the name of TiP-Offnlounts, do away with the necessity ofany gunsmithing to mount such a scope
on any rifle which has the Propergrooves. All gun and sight manufactur-ers try to adhere to standard grooveIocations and dimensions. By the use
of gauges they can make both rifles and
scope mounts so that whenever a scope
is put on such a rifle-no matter whatthe . make of either scope or rifle-the scope will be aligned very closelyvvith the bore of the rifle when thescrews are tightened.
Torget scoPe mounls
In the highly comPetitive and spe-
cialized sport of smallbore target shoot-
mounts of great precision. The scopes
are usually about 26" long, and of highpower-l5X to 25X or more-to Per-mit the user to spot his shots withoutrecourse to the sPotting scope.
The scope is held in mounts whichslide onto dovetail-shaped bases, widerat the top than at the bottom, which are
attached to the barrel with small screws.
grooved for quick-attachablescope sight
Some scoPes do not contain anY
method of making range or windageadjustments, but have the crosshairs orother reticle permanently fixed in the
center line of the scope. They depend
on moving the entire scoPe in its
mounts for range and windage changes.
This tends to make the scoPe rugged,simpler in construction, and easier towaterproof. In addition it eliminatesone of the most troublesome problems
of scope-sight construction, which is
how to make the reticle follow the ad-justing screws accuratelY.'
In those scopes having internal ad-justments, the elevation adjtrsting screw
is arranged to push the reticle down,and the windage screw to Push it tothe left. For the opposite motions, thatis, upward and to the right, the makerdepends on a sPring located so as tobear against the left lower segment ofthe reticle holder, to keep it alwayspressed upwards and to the right. Inpractice, it is found that this spring isnot always effective in making the reti-cle follow the adjusting screws whenthey are turned uP or to the right'
It is easier to make the adjustmentspositive when they are incorporated inthe mount. To move right, You canloosen the screw on the right of themount and force the mount over againstit by tightening the left screw. This ispositive, but not as convenient as theusual elevating and windage knobs'
Several different systems are used toincorporate the range and windage ad-justments in the mount. One popularsystem involves the use of a bridge-type mount base with the rear ringadjustable from side to side by 2 op-posing screws, and an arrangentent bywhich the whole rear end of the mountbase may be raised or lowered a certainamount by means of a graduated disk
with serrated edges which screws up ordown on a threaded stem, with a sec-
ond disk below it, also threaded onthe stem. When turned, the lower ofthese 2 disks lifts the rear end of thesight base, and the upper disk is thenscrewed down to lock the adjustment.The sight is held on the base bY theusual split rings. The front one is piv-oted at the bottom so the scope is freeto swing a bit to follow the windageadjustments.
Another system of mounts for scopes
with fixed reticles has what amounts toa pair of V's fixed onto the receiver byscrews, in which the scope is held bythe tension of a spring plunger lyingbeneath the scoPe tube and held bY
the front and rear rings. This spring ac-
tion permits the scope to be snapped in-to the mounts in an instant, or to be
quickly removed if desired.With such mounts, the V's in which
the scope lies are formed by a pair ofspool-shaped cones in the front mountwhich are adjustable for windage and a
similar pair in the rear mount adjust-able for elevation. It is claimed for thistype of mount that it permits the use
of one scope on 2 or more rifles, withno change in the scoPe, bY simPlYzeroing it for each rifle by means of theadjustments on the mount. When thescope sight is taken off one rifle andplaced on another, it should then stillbe in zero in the second mount.
Scope mounts for rimfire rifles
We find that manY small inexPensive
cal. .22 rifles are used for purposes
which do not justify the cost of a high-grade hunting sight with its mounts.Moreover, the low recoil of the .22
makes it unnecessary for the scope tobe as rugged as if it were to be used on
a high power rifle, and also makes un-Scooe for .22 rimñre rifle complete with' quick-attachable mount
l3
Receiver
USING A TARGET SCOPE
nrovc point of irnpact approrimatelv 12lZr.uinntes. It's thc sanlc as rcacìing a rni-cronlcter, so that yon have 25 gracluationsou tìrc barrel of thc adjusting knob andcach big divisiou is also 25. Evc¡v fou¡thdivision is nlarkcd so thal it has'the nu-mcral one or nrìrDerâì two, incìicating 100or 200 divisions on the kuob. In thisnìâlncr, it is very easy to get scope set.tings for any rifle ancì recorcl thc¡r tìresenìc as you do for iron sights.
When foctrsing your scope for anv dis-tance, you must be sure that parallax istakcn out of thc scopc for each distanccand thc sctting for eaclì distancc is rc.co¡dccl. Usually the graduations on thescope tube do not exactly coincide withyour own particular evcsight, so that you¡nnst focus it for each clistance and recor<ìyour settings. The same gracluation scalc
lpplies to thc focrrsing of thc objectivclcns and is markccl on thc outsidc slecvc.I keep track of ting at a zeromarker if I aur s
then recordingrevolutions pluson thc sìeeve, either torvard rre or awayfronr rne, frorn the zero or 50-l,ard sctting.
The sar¡e is true of tlre 100¡,a¡d set-
c targct. You then lookscope, rnoving yorlr cyeforrvarcl anc'l noticing the
he crosshairs on the targct.shairs seem to nrove on the
mirage and dust the sight picture will blurout on you. I've never found.this to bethe caseand have been verv satisfied withthe Z5X.-Anrnun E, Cóor.
Target scope on match rifle
The front mount is a ring which en-circles the tube, arranged to slide onthe scope tube, and a 7s " wide ribwhich extends for several inches alongthe forward part of the tube on top,called the Pope rib after the late HarryPope. This rib prevents the scope tubefrom rotating in its mounts and keepsthe scope upright. The rear mount is aframe surrounding the scope tube, witha spring plunger which presses the scopeupwards and to the right, and with agraduated micrometer head whichpushes down against the spring actionto give elevation adjustments, and awindage micrometer head exactly likeit on the right. The housing which holdsthe elevation and windage micrometerscrews is split and arranged so that itcan be drawn together by a small screw,to clanrp the adjustments against changeonce they have been made.
Just as on a machinist's micrometer,the threads on the elevation and wind-age screws are 40 to the inch, and thebarrel of each micrometer head has 25graduations around its rim, so that eachgraduation moves the screw l/1000".There is also a spring detent givingclicks which can be both heard andfelt. There are 50 clicks to each com-plete turn of either the elevation or thewindage head, so that each click rep-resents a movenlent of Zu tbousandthof an inch, or 7+ nrinute.
It is normal for the bases on whichthe front and rear mounts slide to bespaced 7.2" between centers. As thereare 3600" in 100 yds,, this distance of7.2" is just 1/500 the distance to the100-yd. target, and a movement of thescope tube of l/1000" at the rearmount results in a change of point ofaim of Vz minute, oÍ Vz" at the 100-yd.target. Of course it is also Vz minuteat any range whatsoever, so that achange of 1/1000" at the rear ntountwill move the shot a distance equal to/2" ntultiplied by the number of hun-dreds of yards in the range: Vq" at 50yds., 3/+" at 150 yds., 1" at 200 yds.,and so on.
Of course other spacings betweensight bases may be used if desired. Forscopes that are very long and heavy at
the front end, longer spacing betweenbases has the advantage of supportingthe scope better with less overhang. Aspacing of 9.0" between mounts willgive .4 minute per graduation oÍ .2minute per click; a spacing of 9.6" willgive 3/e minute per graduation or 3/ 16minute per click, and a spacing of10.8" will give Vt minute per gradua-tion or /o nrinute per click.
The graduations on the nticrometerheads of the target scope mounts per-nrit the exact recording of the sightsetting for any range or set of condi-tions, and the target shooter carefullykeeps a record in his notebook of thesight setting for each range and type ofarnnrunition. If the scope sight is to beused on more than one rilìe, he cantarget it and record the settings forevery rifle he owns. In putting a targetscope on any rifle, he should turn upthe locking screws snugly, avoiding theuse of excessive force and being carefulto use the sante degree of force eachtime he tightens the screws or else hiszero may change.
Dehorned mounts
For varmint shooting the best typeof scope is similar to the target scope,and target scope mounts are suitable.However, some varnrint shooters objectto the high thimbles of the adjustmentscrews. One varmint mount is madelike the target mounts except that theadjustment drums are removed and re-placed with a shorter type which is lesslikely to encounter interference. Theyare handier as for size, but not as easyto read and record the elevations andwindages. I
14
(1.) rear mounr of target scope sight (r.)de-horned rear mount for vármin"t scopê
TELESCOPE SIGHTS
TN choosing a scope the first thing isI to decide just what You want it for,and that will put You on the waY to a
decision as to what scope to get.
If it is for a rimfire plinking rifle orsmall pest killing rifle, the problem is
simple. Try if possible to get a riflewith receiver grooved for a quick-at-tachable scope mount which comes al-ready attached to the scope and gauged
so that the scope is well lined up withthe bore as soon as it is attached tothe rifle. Your sporting goods store willshow you several inexpensive smallscopes of 4X magnification with a tip-off or similar mount. Get a scope of thistype preferably with a name that means
something to you, that you have heardbefore, or that your dealer can recom-mend. In buying a scope, the reputationof the maker is imPortant.
If you need the scoPe for targetshooting, you will have onlY a fewchoices. The main points to decide are
the magnification and the diameter ofthe objective lens.
Mognifying PowerAs to magnifYing Power, actuallY,
8X or lOX is good enough for the finest
target shooting, but of late years higherpowers have come to be popular' Tleyñave the great advantage of permittingthe shooter to spot his shots withoutusing a spotting scope, which relieveshim of the disturbance of his shootingposition incident to leaning over to lookihrough it. This can be important insaving time and maintaining shootingposition in a match'
To be useful for sPotting shots at100 yds. at least l5X is necessary, and
20X or 25X is better. The verY highmagnification has some disadvantageundìr conditions of heavy mirage, butmost shooters seem to prefer to cope
with this rather than with reduced mag-nifying power. We suggest that if youwant a scope for serious target shoot-ing, you select one with a magnificationof 20X or 25X. A bench-rest shootermay prefer a 30X scope. High magnifi-cation means a small exit pupil and a
decrease in illumination, However, a
large objective helps the resolving pow-
Part 4 of 4By Moi. Ge'n. J. S. Hotcher, USA (Ret'd)
NRA Sroff
er. A 20X, 25X, or 30X scoPe shouldhave an objective of about lYz" diam-eter; a 12X to 15X scoPe an objectiveof about 1r/¿", and an SX or 10Xscope may do with a l" objective,
There is available a variable-powertarget scope sight that permits changingmagnifying power to any desired figurefrom 24X to 6X by a simPle twist ofthe magnification adjustment collar'This can be very handy when poor con-ditions of mirage, etc., make a veryhigh magnification difficult to use.
Choosing o hunling scope
In making up your mind just whatcharacteristics you want in a huntingsight, it must be remembered that mag-nifying power, width of field of view,eye relief, and adequate illumination, orrelative brightness, are all mathemati-cally interrelated, so that a change inone will affect all the others.
In general these qualities will dependto a large extent on the magnifYingpower that is chosen. With a low-mag-nifying power, you will get a widefield of view, long eye relief, and largeexit pupil, resulting in good illumina-tion in poor light.
This statement may seem to imPlYthat the solution would be to get thelowest power scope available, but un-fortunately it is Dot as simple as that.Larger powers of magnification givemuch better visibility than do verysmall powers, There is every differencebetween looking at an animal 200 yds.
away, or against a brushy background,or in poor light conditions, with a
2VzX or 3X scope and with a 4X or 6Xpower. We often see the statement inprint that a low Power of magnifica-iion is necessary for good seeing indeep twilight or under shade, but thatmuch-copied statement simply isn't so.
Provided the objective is of a reason-
able size, objects can be made out muchbetter under poor light conditions withscopes of higher powers. Many hourshave been spent with a number ofscopes of different Powers lined uP
side by side observing animals andother natural objects while the day-light faded into twilight, and the twi-
light deepened into darkness. Withrðopet having decent-sized objectivelenses, the higher powers always showed
things up better than the lower Powers'One dark rainY winter afternoon as
night was falling fast, several scopes
rvère lined up on a dark blob just visibleto the naked eye at the bottom of a
large oak tree 150 yds. away' The ZVzX
scope showed a small 'animal' of some
kinà near the bottom of the tree, with a
triangular black spot on the trunk be-
hind it. The 4X scope showed the 'ani-mal' much more clearly; it looked as ifit might be a dog or a raccoon, and the
blacÈ spot beyond it seemed to be a
hollow in the tree trunk. The 6X scope
showed that the 'animal' was actuallya small child, and the black spot was
indeed a hollow place in the tree trunk.The 8X scope showed the child plainly'and also . revealed that he had blue
overalls with the straps over a'red shirt,that he had a stick in his hand, and
that he was poking a soft drink cartonplainly seen inside the hollow in the
i..". it was then not quite completelydark, but all the autos passing on the
road above had their lights turned on'
scope made things 150 yds. away look
Varmint scope mounted on high power rifle
as they would to the naked eye from50 yds.; the 4X scope showed them asthey would look from 37/z yds.; the 6Xscope made them look 25 yds. away,and the 8X scope made them as plainas they would have been to the unaidedeye at l87a yds.
In this test were used a high-grade 4Xhunting scope with a 1" diameter objec-tive, and an inexpensive 4X scope of thetype intended for use oi .22 rimfirerifles, which had an objective only Vz"in diameter, or just one-half the diame-ter or one-fourth the area of the first-mentioned one. As the light began tofade, it became increasingly hard tomake out things with the Vz" objectivescope, and it soon became totally use-less while the one with the larger objec-tive was still giving a satisfactorilybright image. In bright sunlight thesmall scope seented just as good as thelarge one, but as the light failed the ad-vantage of the large objective made it-self decidedly felt.
Fine crosshoirs undesirobleThese tests also sbowed that when
a scope is being used under conditionsof insufficient light, the first thing thatputs the scope out of business is diffi-culty in seeing the crosshairs. For thisreason very fine crosshairs should not beselected for any scope that may be usedbefore full daylight or in deep twilightunless there is also a post available.
Fronr considerations of width of fieldof view and good eye relief, a 4X scopeis probably a good choice for deerhunting and the like, while a 6X mightbe preferred for hunting where thecountry is likely to be open and rangeslong. If there is doubt as to exactlywhat the conditions are to be or whatgame is to be hunted, a variable-powerscope of 2X to 7X, 2z/+X to 8X, 3X to9X, or the like, provides great versatil-ity to n.reet a variety of conditions.
Another question which may arise iswhether to get a hunting scope with in-ternal adjustments or one with thereticle in a fixed position and with theadjustnrents in the mount. Targetscopes, of course, have the adjustmentsin the mounts, and nrost of the earlyscope sights used in this country hadmounts just like the modern target scope.
As a result of years of use and ex-perience, the public preference seemsto be for internal adjustments, but oneplace where it is best to get a scopewith fixed reticle and adjustments inthe mount is when it is desired to useone scope on 2 or more rifìes. In thatcase each mount can be zeroed so thatwhen the scope is on that rifle it wiltshoot where the gun aims. The scope,having no adjustments of its own, canbe freely changed from one rifle to an-
ló
other and still retain its individual zerofor each rifle.
The stock of a rifle which is to beused with a scope sight must be soshaped as to hold the shooter's eye ex-actly in line with the axis of the scopewhen the gun is held in shooting posi-tion and the cheek is held against thestock. Because the scope sits higher thanthe usual iron sights, most rifles conrewith stocks that are too low for best re-sults with scope sights, and the riflenrust be restocked or a higher cheek-piece must be attached. Some huntingrifles and most high-grade .22 targetrifles now come with stocks speciallyshaped for use with scope sights.
In nrounting a scope sight on a riflefor the first tinre, care should be takento place the mounts so that the reticlewill be at or near the center of its ad-justment when the scope is zeroed.
With some scopes the nrotion of thereticle is visible. The crosshairs can beseen to go up or down as the elevationknob is turned, and to move to one sideor the other as tbe windage knob isturned. With such scopes the reticleshould be visibly in the middle of thefield of view, cutting it into 4 equalquarters. But some scopes are made sothat the crosshairs always bisect thefield, and do not seem to move as theknobs are turned. To get the adjust-ments centralized on scopes with thisconstruction, first set the windage knobto the center of its range by turning itas far as it will go in one direction,noting the reading and then going asfar as possible in the other direction,then back to the halfway point. Repeatthis with the elevation knob.
Slight convergence desirobleWhen a scope which has had the
reticle brought to center in this ntanneris placed in its mounts on the rifle, theoptical axis of the scope should beparallel with the axis of the bore of therifle or, as a refinement, should con-verge toward the axis of the bore tonreet it at about 25 yds. from the nruz-zle, thus autonratically adding a slightanlount of elevation. If the axis of thescope does not line up in this way. itmay be necessary to change .the posi-tion of the mount bases slightly byshinr nting.
This is best checked by boresighting,which nreans lining up the rifle with thetarget by Iooking through the bore.Place the rifle on a steady rest pointingin the general direction of the target.If it is a bolt-action rifle, take out thebolt and look through the bore, andline up the rifle so that the target canbe seen through the bore and appearsto be exactly central with the bore. Ifit is a lever-action rifle, open the breech
Bore sighting, showing view through borewith target in distance
and look through the bore by nreans ofa bore inspection mirror. As a refine-ment to perntit easier lining up of thebullseye to a central position, the boltwith the firing pin removed can be leftin place and the firing pin hole in thebolt can be used to sight through; or anempty cartridge case vvith the primerremoved can be similarly used.
After the rifle has been lined up inthis way, look through the scope with-out moving the rifle. The crosshairsshould be on the bullseye. If they arenot, the necessary correction in the po-sition of the mount bases should benrade. If it is desired to make the lineof sight parallel to the bore, the targetused for boresighting should be about100 yds. away. If it is desired to add asnrall amount of automatic sight eleva-tion to give a longer point-blank range,the boresighting should be done at 15yds, for rintfire rifles or 25 yds. forcenter-fire rifles.
With the scope in its mounts on theriffe and satisfactorily lined up as justdescribed, the next step is to zero itwith the same ammunition that is to beused with the gun and sight.
It nray save ammunition and preventthe risk of nrissing the paper before thezero is found if the first shots in zero-ing-in are fired at a short range ofabout 25 yds. Most scopes are not ingood focus for short distances such asthis, but the target can be seen wellenough for the purpose. With the rangeand windage knob adjustments set atzero, aim at the bullseye, and fire ashot, then make the necessary rangeand windage adjustments to bring thepoint of inrpact to the point of aim.When this is satisfactorily accon.rplishedloosen the small screws that hold thenrovable index plate on the windageand elevation knobs, set these indexplates to zero, and re-tighten the screws.
Next, nrove back (or move the targetforward) to the average range at whichyou think you are likely to do most ofyour hunting with this rifle, and repeatthe process of sighting-in. Then recordthe readings of the range and elevationknobs, place the caps over the knobs,and screw thent down tight.
I lI
-r'n- 15
'{rr. ..¡Í{;i:--"--"I I-==l--
r¡ J);r)Once You getits scoPe sight taadjustments andwith it. When Yohave those recorded readings of the
elevation and windage at hand. Thelast thing to do before setting out to doyour actual hunting is to check them.
Torgei scoPes ond mounls
There are a few Points in which thetarget scope sights differ from the hunt-ing scopes in their use and adjustment.These concern the eye relief stop, the
reticle adjustment, and the parallax
adjustment.Unlike the hunting scope sight, which
has no backward and forward motionrelative to the rifle once it has been
placed in shooting position, the target
À.op" .un slide backward and forwardin its mounts.
Just forward of the front mountthere is a clamp ring on the scope tubewhich limits the distance the scope can
be pulled to the rear. This is the eye
relief stop or clamP ring.After the scoPe has been Placed on
the rifle, the eye relief clamp ring screw
should be loosened and the ring should
be pushed forward out of the way. Then
lie down in prone shooting position,
using the sling, and Pull the scoPe
back until it is at just the right distancefrom the eYe. Without moving the
scope, place the eye relief clamp ringagaìnst the front mount, and tightenthe screw. When the gun is fired, the
scope will slip forward a bit from the."cõil. After each shot it must be pulled
back until the eye relief stop ring is
against the front mount' The distancefrom the ring to the front of the scope
or to the place where the tube starts
to enlarge for the objective lens shouldbe recorãed, so that if the gun is used inany position other than prone, the ringcuá Ue reset to its proper place withno trouble. If the gun is also to be
used in the standing position, find theproper location of the ring to give theright eye relief in the standing position,and record that also.
Another adjustment that must be
made on target scopes is the leveling ofthe crosshairs. The reticle is containedin a hotder which slides inside of thescope tube just in front of the eyepiece,
and is held against rotation by 2 set-
screws which can be seen, one on each
side of the tube, in a serrated ring lo-cated just forward of the eyepiece.
When you are in Your Preferredshooting position, look at the cross-
hairs and see if the horizontal hair ap-pears level. If not, loosen the 2 set
screws. Turn the leveling ring until thehorizontal crosshair is level, tighten theset screws, replace the eyepiece, and
refocus the scope,
Parallax adjustment on a target scope.First loosen the forward serrated ring,
firmly to lock the adjustment
of the lens, and turning the lens nrightthrow the line of sight off'
To remove parallax for anY givenrange, place the rifle and scoPe on afirnr rest pointed at a target at the exactdistance for which you desire to cor-rect the parallax. You should have al-ready focused the eyepiece until thecrosshairs are sharP and black'
Observe the target and move thehead front side to side, to see if thereis any apparent movement between thereticle and the in.rage of the target'lf there is any such movement, parallaxis present and nrust be removed. If the
image of the target moves left in rela-
tion to the reticle as the eye is movedleft, or in other words if the image ofthe target seenls to nlove with thenrovement of the eye, then the objec-tive is too far forward' and must be
moved back, and the opposite holds ifthe apparent motion is the other way'Loosen the lock ring, screw the sleeve
back a bit, then tighten the lock ring'which will force the objective to the
the front of the sleeve.
ain, and continue until allone. Now record the Paral-for that range, using the
graduations around the rim of'the sleeve
in conjunction with the range gradu-
ations on the body of the scope' Makethis adjustment for each range at whichthe scope will be used, and record them.
The ìarget scope has caps, usually ofthe screw-on variety, to cover boththe objective lens and the eye lens'
These should be kePt in Place when-ever the scope is not actually beingused, to prevent grit and sand fromblowing onto the glass surface.
Core of scoPe sights
In line with what has just been said
about protecting the lenses, it is not a
bad idea to keep a set of transparentlens covers on the hunting scope sight
Another adjustment found in targetscopes is a movement of the objectivelens to eliminate parallax for the partic-ular distance in use. This is done byfirst loosening a clamp ring just behindthe objective lens, then turning a grad-uated sleeve which extends a coupleof inches to the rear, where the edge
is used as an index for the range scale
engraved on the body of the scope' Thisrañge scale has marks for 50 ft., 25
yds., 50 yds., 100 Yds', and 200 Yds'or over. The markings may vary slight-ly on different makes.
Locking obieclive lens
The front or locking ring holds the
sleeve as a stop, where it can be lockedby screwing the lock ring tight.
In its motion forward or back, the
objective lens slides straight forwardor back and does not turn. The turningof the lens is avoided because it is
not always possible to get the opticalaxis exactly in the physical center line
Correcting parallax by movin e both screws
holdins reticle turret (shown knobs)' Then
;ääiiö"ì'ri; äiìãi.'äì."' ror parailax'
and repeat
i4erd¡
[¡
l-
aa
"Here's how I did it"
Transparent covers protect objective andocnlar lenses from rain, snow, and dust
when it is not in use. This will keepthe lenses from getting covere<I withdust, and will obviate much lens wipingwhich otherwise would beconre neces-sary, and which cloes nothing to helpfine optical surfaces.
Sonre scope covers are made of thinglass free frorr any optical effect, andit may be desirable to leave thenr inplace when hunting in foggy, rainy, orsnowy weather until the nrontent thatthe scope is actually to be used. In anemergency one can shoot with them inplace on the scope.
Protect the scope sight against jars,jolts, ancl dropping. A fatl onto a tilefloor may shatter the objective lens.
Never take the scope apart if it canpossibly be avoidecl. The scope sighthas been put together in a factorywhere the air has been filtered and isdr-rst and ntoistr¡re free, ancl no dr-lst canget insicle if the scope is not opened.
Modern hunting scopes are often fog-proofed at the factory, which lneansthat they are assembled in a dry atmos-phere. or perhaps filled with dry nitro-gen g¿ts, and then sealed around theadjustnrent turrets and the eyepiecethreads. Such scopes will stand evenprolonged exposure to a hard rain with-oLrt fogging, but one precaution is inr-portant-the scope shorrld never besubjected to any more change in tem-perature than is unavoidable. A scopecarried all day in bitter cold weatherr¡,ill have rnoisture condensed on it ifit is brought inside a warm builcling ortent. If it is kept inside overnight sothat it is thoroughly waln and the airinside it is warm, and then taken outinto a cold rain, the warm air inside thescope will contract and the partial vac-tuunt inside will cause air- ancl moistureto be pushed inside.
When you come into a warnr placeafter being out in the cold all day,leave the rifle outside. If vou n.rustbring the rifle in, wrap it in severalthicknesses of blanket first, to avoid asmuch as possible any violent tenlpera-ture changes.
In short, cover the lenses when pos-sible, avoid jars and falls, do not iakethe scope apart, and avoid tentperaturechanges. If you will pay attention tothese small precautions, your scope willserve you well. Il8
I wished to mount a scope with aclaw-type mount on a cal. .22 rifleleceivel without grooves and had nomachine-tools available. I cut a dove-tail block into each end of the re-ceiver fal enoLrgh to the left to givebolt clearance. This can be done with
a 3-cornered file.-Rnlpg Coore
, very hondy diogrom con be mqde ondottqched lo the scope iube lo show ol oglonce iusl how for obove or below theline of sight your bullet will be ot onyronge. Obtoin lhese figures from on om-munition hqndbook for eoch rqnge youwill be shooting, ond loy them out onwhíte poper to q scole of Ya":|". Pholoshows the one on my own rifle whensighted in ot 2ì0 yds.
Cul poper to size ond opply 2 coqls ofcleor locquer to protect it from hondling.Apply rubber cemenl lo poper ond scope,ollow borh to dry, ond then press popertightly into ploce. lt will odhere wellond still be eosy to remove when desired,
-Robert V, Thompson, Clinton, lowo
t015 20
25
30
Riflemen using the B&L riflescope ondmount ore foced with the necessily of re-zeroing whenever lhe lood is chonged,since lhe mounl contoins no provision forreoding settings ond relurning to them, Iexlended every fifth mork oul to the edgeof the sight bose, then filled these, qndolso lhose on the movoble diols, withfingernoil polish. By counting the mqrksclockwise, q recordoble figure is obtoined,Different colors con be used for lhe elevo-lion qnd windoge sides, to help in ovoid-ing interchonging the doio.-John C. Mc.
Aleovy, Modison, Wis.
eofcope
thethe
wasformed flom heavy gauge soft alumi-num with edges crimped to fit scope-ring blacket. Flathead screws wel-e
pistol box coverews act ¿ìs stops.
when scope isst stop screw.-
JoHN W. G,rno¡.lEn
Hn¡rirfl-
5
To mount a Weavel scope with N5mount on an M1853 Enfield rifle-musket withou[ altering the weapon, Isoldeled an extension to the front ofthe mount so that the lockplate screwscan be used. The extension is tbe samethickness as the mount. The rearmosthole in the mount is enlarged to fit therear lockplate sclew, and this is thepivot point for elevation adjustment.The front lockplate screw' extendsthrough an elongated hole in the mountextension, and clamps the mount inposition. The scope is slightly offset tothe left which I find ideal for astraight-stocked musket.
To install Weavel top scope mount onrny 0343 Springfield, I modified theService lear sight base as shown.Weaver base (3/16" height) was thenattache<l with two 6-48 screws so thatsclew ends bore ageinst receiver, secur-ing assembly against movement. In-stallation of No. 55 Weaver base onreceiver ring completed the job.-
BrnN¡n¡ J. Pn¡cp,
Choosing
and tlsinga, Spotting
Scope
1 Hieh-erade - p_rism spotting scopes. These, and the prism scopesI illustrated below, are the finest and most desirable- instrumeits
available for target spotting
r¡ Some prism spotting scopes have the eyepiece set at an angle forz convenience in viewing from the shooting position
^ cooD spotting s
fl necessary articltlie target shooter, bful to the hunter astain circumstances a Z0-power scope ona solid mount will tell the long-rangehunter things that no binocular will.
Over the years the design of spottingscopes has undergone a process of evolu-tion ând standardization until todaymost represent designs which are justwhat long experience has shown the
as a target spotting scope and you willavoid disappointment. The cheaply-made imported draw-tube scopes of the'spy-glass' type sold by cut-rate storesand mail-order advertisers are entirelyinadequate for target spotting, and willonly prove to be a disappointment ifpurchased for this purpose.
settled, and the decision should dependon the purchaser's pocketbook. A draw-tube spotting scope is all that is neededby tbe pistol shooter and will givesatisfactory service to lhe rifleman also,but in this field, as in most others, you
r9
Æ
2 Draw-tube .spotting scopes are less expensive than the prism type,iJ but are quite efficient and satisfactory-. They are lisht ãnd hanãv.and when closed are short enough to fit inio smallisize pistol kiló
<4themotheremoving .the scope from the mount. The high-grade draw{ube spotting scope
beside the kit box can also be mounted and used in the samè way
t On the rifle range a stand for the spotting ¡¡, scope is a necessary accessory. Stand Zshown on the riSht is cleverly designed toavoid any possible interference with the
shooter's elbow in the prone position
getthecertain advântâges.
Where the larger ancl hcavier prisrnscopes hâr¡e the aclvantage is in thesomewhat better definition ancl light-gathcring power ancl the largcr exitpupil, permitting less critical e),e posi-tion, nacle possible b), tl.te larger objec-tivc; ancl in a larger fielcl of vier,v, en-abling the user to see rllore on cach sicleof his own target. The fielcl of the usualcl¡aw-tube spotting scope is about 7 to7Vz ft. at 100 ycls., while that of theprism scope will be perhaps I I ft. atthc same cìistancc.
On the othe¡ hancl, the cl¡au'tubcspotting scopcs, l.raving no prisnrs withtheir critical acljtrstments, arc lcss bulky,lcss likely to get out of order, ancl a¡esimpler to clc¿rn ancl casier to repair ifanything cloes go wrong. Morcovc¡, theyare lighter ancl hanclier, ancl rvill fit intothc smallest size pistol shooter's kit box,which most prism scopcs will not.
Thc qucstion of nragnifying porver isonc thing tìrat thc purchascl of a clrarv-tubc spotting scope rvill not have to cle-cicle. Ifc will take 20X ancl likc it, forall cl¡aw-tubc spotting sco¡rcs on thernarkct are of this powcr, rvhich longexpcricnce has shou,n to bc the mostall-a¡ouncl desirable ancl satisfactorypou,cr for this purpose.
In prismatic spotting scol)es, therc is
sorne latitude as to n.ragrrifi'ing power,for rvhile rnost of them are norrnallv of20X, there are sorile that mn slightly
20
higher. Of l2 prismatic scopcs invcsti-gatecl, 7 were 20X, I was 22X, 2 were24X, ancl 2 we¡e 25X. There is little tochoose between theur. The little bit ofextra magnification is nice, but one p¿tysfor it in reducecl fielcl of vierv anci ie-clucccl exit pupil, requiring more definitepositioning of the eve behind the eve-piece. Some high-grade prism spottingscopcs câll l¡e fu¡nishecl at extra costrvith l5X, 25X, 30X, 40X, ancl 60X
amatcur astronorny. For target spottingthc 20X wilì be the one most usedsincc a 20X in a clrarv-tube spottingscope r,vill shorv u¡r .22 cal. bullct holesin the black of the target at 100 yds.uncler excellent light conclitions, while20X with a larger objective prisn-r scopelvill sholv thcnr cven l4ren the light isnot too goocl.
To focus thc scope, the eyepiece rnustbc adjustecl in ancl out. Most of thespottiug scopcs on the market, whethe¡prism or drarv-tubc, have a coarsc focus-ing acljtrstrnent bv simply pulling outor pushing in the eyepiece to nc4rlvthe right placc, after rvhich a fine adjust-ment is accornplishccl b), tu¡ning theeyepiece, rvhich u,orks on a quicklitchthreacl. I-los'ever, in two high-gracleprisn.r scopes, the focusing is bv a
knurlecl knob which rìloves an internal
nrember to make the adjustnent. Thisis a very satisfactory system.
In focusing any telescope or binocu-lar, bcst results will be obtained by start-ing with the tube pulled as far to therear âs possible, and then moving itforwarcl until the image becornes clear.In scopes which are focused by turninga knob, move the knob so the scopeis focused or1 sonle nearby object, thenpoint it at the object to be viewed, anclturn the knob until the iurage clearsuP.
Most spotting scopes have the eye-piece in line with the longitudinal axis,but one is rnaclc with a right-angle eye-picce, which makes it easier fo¡ a seatedobserver to rvatch proccedings from a
comfortable position, ancl is hancly forthc prone shooter, who can look throughthe scope by sirrply turning his heaclwithout rnovir.rg his bocly. Sorne prisnrscopes âre also macle with eyepieces setat 45' for the sanle purpose. Thescangle eyepieces are unclotibtedlv con-vcnient, but thcv do make the scope a
bit more clifficult to airn. The purchasershoulcl, if possible, try both kinds beforcbuying.
A spotting scope is not courpletcwithout a stancl of some kincl. Mostscope rrakers sell stands for their spot-ting scopcs, and several acccssorl, dsxl-ers also sell stancls especiallv clesigneclfor the prone shootcr. The pistol shootcrusuallv fixes a scope holcler insicle thclicl of his kit box. ancl needs no otherstancì for his spotting scope.-r
just about whatDlore exPensrve P
younslll
Pay for,clo
anclgivescoPes
.*"{', '*?4
ì
A
Selectingand LIsingBinoculars
inabof
is what magnifying power is best forthe particuìar use to which the glassis to be put. The basic reason for a
binocular is to make things look closer,and it accomplishes this by magnifyingthe image. A glass that makes things
¡.r These oictures show the difference betweenZ standarà and extra-wide field of view. PictureE shows 2 deer as viewed through a 7x35 binocu-lar having a'llzo fi 000yds,, whiõh may be forihis'power. PiCture thesamá distance when ide-field field of l0', or 525 ft. at1000 n that the wide field givesimpo nder some conditions, butthele be paid for in increasedweight, bulk, and cost of the instrument. In gen-eraf a'7x35 binocular with a standard field widthof Ttho is a splendid compromise, and should
serve well under a variety of conditions
look 6 times their natural size is calleda 6-power, and is marked 6X; likewisea 7X or an 8X glass will enlarge obiectsviewed 7 times or 8 times, respectively.An object that in reality is 300 ft. dis-tant will seem to be only 50 ft. awaywhen viewed through a 6X binocular,4l ft. through a 7X glass, and 37 ft.through one of 8X.
Limits on mognificotionAt first thought it might seem that
if some magnification is good, morewould be better, and the highest magni-fication available would be the one toget. This, however, is a mistaken idea.It overlooks the fact that increased
power must be paid for in several ways,such as less steadiness, reduced field ofview, and poorer light-gathering power.Very important is the increased dif-fictrlty of holding the glass steady rvhen
is necessary for satisfactory viewing.The fieid of view is tÉe portiõn of
the landscape that can be seen throughthe binoculãr without moving it. Thisdecreases in direct proportion to themagnifying power, so that an 8X glasshas only 7/+ the width of field that a
21
6X glass has. As width of field is quiteimportant under some circumstances,this reduced width with higher powermust be carefully considered. Anothereffect of increased magnification is tocut down the relative brightness. Thisfactor, which is fully explained below,falls oft very fast with increasing magni-fication, so that a 6X glass has 4 timesthe relative brightness of an 8X glasswith the same size objective.
Balancing theoretical considerationsand tests with long years of experiencein the field, most armies have adoptedthe 6X binoculars as standard, whilefor naval use 7X glasses are favored.
Xtobe
"'ffiå:gafe-spectable amount of relative brightness.
Binoculars are named by magnifica-tion coupled with objective diameter inmillimeters; thus, 6x30 means a 6-power glass with an obiective J0 mm.in diameter. The size of the obiectivehas a tremendous effect on binocuìar
or at night, in-
fffii:'H'i::with a binocular.
As the amount of light gathered byan objective is proportional to the lenssurface, ancl as this in turn is propo¡-tional to the square of the lens diam-eter, it can be seen that for the samemagnification a glass with a 50-rnm.objcctive will have 2.8 times the relativebrightness of one with a 30-mm. objec-tive. It will, however, be much bulkier,heavier, and more expcnsive.
The light fafling on the obiectivepasses through the opticaì system andcomes out through the eyelens in acompact bundle of rays callecl the exit
Thus, a 6x30 binocular has an exitpupil 5 mm. in dian-reter, and the rela-tive brightness is 5 squared, or 25. An8x30 has an exit pupil 3.75 mm. indiameter, and a relative brightncss of14. A 7x50 glass has an exit pupil 7.14mm. in diarneter, and a relative bright-ness of 51.
22
of the eye. If it is larger than the pupilof the eve, some light will be vvhsted,while if it is smaller, then the eve u'illnot have all the light it can use, andthe image will tend to be dim.
Studies have shown that the pupil ofthe average human eye may have a di-ameter of about 3 mm. to 3.5 mm. or a
brightness, while for night use a relativebrightness up to 50 can be utilized toadvantage.
Besides the size of the obiective anclthe rnagnification, the¡e is one othirin.rportant item which can have a pro-founcl effect on the brightness of theimage, ancl that is the efficiency withwhich the light passes into and out ofthe various.optical elements inside theglass. Each time a light ray enters orleaves a glass surface, it loses about 5Vothrough reflection, unless the suiface istreated by optical coating. It is easy totell at a glance whether or not the out-side lens surfaces are coated, by observ-ing the reflectibn of the sky or an over-lread light. If the surface is coated,there will be a bluish or purplish colornoted. This does not, however, tellwhcther or not the various inside sur-faccs are coated, and in a prism bir.r-ocular thev are the most important forour investigation of the coâting ques-tion. The best way to handle this is tobuy only from a reputable source, andto require the seller to state in the billof sale that all the optical elements arefully coatecl.
In the specifications fo¡ binoculars,you will encounte¡ the ie¡ms fielcl ofview, wicle freld, extra-wide field, etc.The wiclth of the fielcl of view of a
binocular is usuallv stated in feet ofwidth at 1000 vds. from the observer.
It has alreacly been indicated that thcfielcl of view of high power binocularsis less than it is with a lower powerglass of silnilar construction. For the6X glass of conventional design, thefielcì of view is al¡out 445 ft. at 1000yds. ancl that of the 8X glass of thesame construction is about Il0 ft.
The size of the objective lens clocsnot afiect the fielcl of. view. That isdetermined principallv bv thc clesignof the evepieces, plus sonre neccssârvincrease in the size of the prisrns. Extra-wicle-fielcl binoculars, with their spe-cially constructed ancl clcsignccl cye-pieces ar.rcì their larger prisrns, a¡c rrat-uraìly rnore expensive and bulkier[han glasses rvith t]re nonnal construc-tion and a fielcl of view of avcragcwiclth. N,Ioreover, it is excecclingìv clif-frcult to gct a very rvide field of view
without some distortion near the ecìgcsof the field, and it will be founcl withmost, if not all, extra-wide-field bin-oculars that straight lines near theedges of the field of view appear curved.To many, this efiect is no[ too objec-tionable.
To the man who may have to carrva binooular in its case suspended fronrhis neck for hours at a lime, weightand bulk become factors to be con-sidered. A normal 6x70, 7x35, or 8x30binocular in its case will weigh in theneighborhood of 2 lbs., while a night-glass type with 50-mm. objectives iviìlweigh perhaps 3 lbs. or more. Somcmakers employ magnesium alloy forthe frames of their binoculars, ancl thuscut a few ounces f¡om the wcieht.
There are very small binocular-s avail-able at mocleraie prices, which weiglrgdly a, few ounces and may ,be carrieclin a shirt pocket without ôases. Theseglasses with 6X power and 20-mm.objcctives, are very useful for certainpurposes, and are at their best for uscin bright sunlight, where the \¡ervsmall light-gathering powcr of the littlc20-mm. obiective mav be sufficicnt forrnost practical purposes.
lmporled binoculorsBinoculars which fronr the outsiclc
look vcrv much alike come in a rviclcrangc of prices, but in this field, pcL-haps more than in most othcrs, ii isirnportant to remember that )¡ou gctiust about what you pay for. AfterWorlcl War II, the fapanese went intothc rrranufacture of binocuìars in n bigwar,, and great numbers of f apanescglasses have been imported into thcUnitecl States in recent vea¡s.
The fapanese have the ability to makeexcellcnt optical goocls, ancl their bestmakcs a¡c brought into this country bvso,cral high-gracle importers lvhothrough rigid specificatior.rs, throughinspection cluring rnannfacture, ancl a
final going-ovcr aftcr thc goocls arrivcin thc U.S., take pains to assure a gooclprocluct. Thev stancl bchincl their irr-portations,. ancl guarantce to furnishrepair sen,ice in cases lvhere it becornesneccssar\/.
IIou,cvcr, in fapan thcre are uranyrnakcrs, aucl some secnr to pav littìcattcntion to rigicl constrnction or gooclworkmanship. The proclucts of the seshops, as welì as the glasses lnaclc bvthe l>ctter maker which r.lrav be rejccteclbv the importcrs mentionccl above, arcall importccl in large guarrtitics. Thuschcap unsponsorecl binoculars of fapa-ncsc n'rake lnav be founcì just al>outcvervrvlrcrc. 1\4anv such gìasscs of gooclappc¿lrarlcc can be hacl for priccs as ìorvas $25 or lcss, ancl thc'r, lrav pcrfornrwcll for a timc, but thc cor.rst¡uctior.t is
usuallv flimsv, and once they get out-ofadjustmcnt ihe owncr is strictly on hisown, for the selle¡ is no longer inter'ested. It may well cost rnore than the
mail from a reliable house which offersa money-back trial period of sufficientduration.
After a binocular, the nextIf it is anthen pro-type'
First turn each eye-
t Binoculars are eraduated for inter-
'l pupillary distancé in millimeters ontop of the center hinge (l), and for indi-vidual eye corrections in diopters on thebarrel of each eyepiece in individual focusglasses or on the right eyepiece (2) only incentral focus glasses like the one shown
tance between the pupils of the eyes inmillimeters. This number is called theinterpupillary distance. Each pe rsonshould dete¡rnine and record his inter-pupillary distance. If you buy your bin-òcular from a store, the dealer willgladly holcl a nillirneter rule to youreyes ancl tell you what your interpupil-lary distance is. It is normally about65 to 70 urrn.
With the center-focus glass, thefocusing procedure is slightlv clifierentas the left eyepiece cloes not have anvgraduations. To focus such a glass,
proceecl as follows. Turn the focusingwheel until the briclge supporting the
ing it. After this is clone, the glass isrefocused for different clistanccs or veryneâr obiects bv sintplv turning the cen-ter wheel. The right evcpiece rvilì nothave to be touched again uuless sotle-
IS itgettingto focus
ceecl âs
glve an excellent guarautee.If one can possiblv afiord the cost,
the satisfaction can be ob-by a top-quality Arneri-
can-macle cafr\¡lng a Iifctimeclosing the left eye ancl focusing theright eyepiece. Now point tltc birrocu-lai at thc skv ancl bencl thc centcr hingeuntil the ciicles seen with the two eyes
ocular and changes the setting. Notealso the setting on the gracluations inthe hinge. These are marked in thc dis-
guarantee. Such a binocular rvill costfrom $155 to $I70 or rnore, and is asuperb instrument well worth the price.
The rnost satisfactory way to buY abinocular is to go iuto ¿rn optical goocls
store where seycral ¡1,pes and kinds are
on sale, ancl trv then out on the spot,
¡rrcferablv gctting permission to takeihem out to the strect for a bettcr look.'Ihc next best r,vay is to bu1, them by
one changes it.
Jr
@ &).-V
Ir( alarl
23
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