Questions & answers
From the thousands of questions and letters on guns, ammunition and their use that the American Rifleman receives every year, it publishes here the most interesting. Receiving answers to technical and historical questions is a privilege reserved to NRA Members.
Questions must be in the form of letters addressed to Dope Bag, NRA Publications, 11250 Waples Mill Rd., Fairfax, VA 220309400, must contain the member’s code line from an American Rifleman or American Hunter mailing label or membership card; must be accompanied by a stamped, self-addressed, legalsized envelope, and must be limited to one specific question per letter. Non-members may submit a question with membership application.
We regret that we cannot answer technical or historical questions by telephone or fax, and that we cannot place even an approximate value on guns or other equipment of any description.
AIRGUN SCOPES
I recently acquired a powerful spring-piston air rifle, on which I mounted a 4X hunting scope I used for years on a .30-’06. Within 100 shots the reticle wouldn’t hold zero. Why would a .177 cal. airgun break a scope that has taken hundreds of full-power .30-’06 hunting loads?
Air rifles and cartridge arms have very different recoil patterns. In cartridge arms, virtually all gun movement is due to recoil, driving the firearm to the rear. Semi-automatics also experience a forward impulse as the spring-driven bolt or slide slams into battery, but this is usually much smaller than the recoil. A different recoil pattern is seen in airguns using air compressed by a forward-moving, spring-driven piston. Such arms have a relatively small rearward push. When the piston reaches the end of its travel, however, it imparts a sizable forward jump to the arm. According to Tom Gaylord in his book, The Beeman RI Supermagnum Air Rif le (available from GAPP, Inc., Dept. AR, 4614 Woodland Road, Ellicott City, MD 21042-6329), this forward motion represents almost 90% of the total recoil force of such airguns. Scopes made for cartridge arms are designed to withstand a sizable rearward recoil impulse, but not a forward onewhich is probably why your scope broke. Breakage is even more likely, Gaylord writes, with heavy, large-objective scopes.
The solution? Get a good-quality, lightweight scope made specifically for use with high-powered spring-type airguns, along with the proper mounts and stop block to keep the scope from “walking” rearward.-S.L.W.
MILITARY POWDERS
I have purchased some surplus M2 ball powder originally made for use in .30-’06 MI Garands. I know it is a Winchester powder but want to know what number it is or what Winchester number I can substitute for it as I want to use it in some other calibers?
I have no way of being certain of the powder you have purchased, but it is probably WC 852. If that is the case, it is a military powder and has no canister equivalent.
Military powders can vary considerably from lot to lot. This poses no problem in military loading plants because military ammunition is loaded to specific pressure and velocity standards with only minimal regard for the amount of powder required. Each lot of powder is tested to determine the charge required to meet the pressure and velocity requirements. The ammunition is then loaded with the required amount of powder. Unlike handloaded ammunition, the amount in military ammunition may vary considerably from lot to lot.
Military powders are not inferior to canister powders. They just have greater lot-to-lot variation.
If the powder vendor cannot provide you with loading data, you will have to develop your own loads through careful experimentation.C.F.
REVOLVER ACCURACY
Seeing as revolvers have a number of different chambers, I was wondering if you have encountered variations among the chambers. What effect does this have on accuracy, and what could cause it?
We have indeed seen instances where a single chamber threw shots that markedly degraded a gun’s potential accuracy. There are several possible causes, including a diameter variation from one chamber to the next caused by tool wear or machine tolerances.
Another possibility is that if the cylinder rotation is not true, one or more chambers may not line up precisely with the bore and lead to deformation of the bullet as it crosses the barrel/cylinder gap.
The most common source of problems seems to be variation in the diameter of the chamber mouth (ball end diameter). Ideally, this should be the same as, or only slightly larger than, the nominal bore diameter. In most cases where it has been possible to identify a single charge hole that throws shots, the ball end diameter has been oversize.C.E.P.
RETINA DAMAGE
l recently read an article about the potential for retina damage from regular shooting of hardkicking rifles. I normally use a 7-lb. .3030. Is there any danger from this?
The retina is the seeing layer of the eye. It is a layer of nerve tissue about 1/50″ thick or less, and it covers the back two-thirds of the eye. It is firmly attached at the front and in a small circle at the back, but not so firmly elsewhere. If it is damaged or separated from the back of the eye, vision is lost at that spot.
A lot of force would be required to separate the retina from a healthy eye-consider prizefighters who take much more punishment to the head than would be provided by even the hardest-kicking rifle.
On the other hand, a variety of conditions can make the retina more susceptible to separation. Nearsightedness can be caused by an elongated eye, which can result in thinning of the retina at the back of the eye around the optic nerve.
This is not to say that retinal damage is inevitable for nearsighted shooters-it’s just slightly more likely.
When having your eyes examined, mention your concern to your eye doctor and have him or her pay special attention to the retina. If you notice any unusual symptoms, such as seeing stars, have an eye exam immediately.-R.B.P.
THE “90” IN .45-90
I have a modern-made .4590 cal. Sharps “1874 Model” and a similar.45-70 rifle. What I need is know is how to load the two rounds. In the .45-90, I plan to use a 428-gr. bullet. I plan to use blackpowder, but don’t know how much and what kind? For the .45-701 have 385gr and 405-gr. bullets. What blackpowder and how much should I use?
The second number in the names of the blackpowder cartridges you list indicates the load. For instance, the .45-90 cartridge employs 90-grs. of blackpowder, and the 45-70 uses 70 grs. of blackpowder. Modern-made cartridge cases may not be able to hold this amount of powder so ensure that enough blackpowder is used so that the bullet, when loaded, will press solidly against the powder. I would recommend using FFg blackpowder or the new cartridge-grade blackpowder.-R.C.
CARTRIDGE PRESERVATION
I recently inherited a nice cartridge collection, but lam getting tired of polishing it and some of the lead bullets seem to be growing a white powder How can I protect them?
Most serious cartridge collectors do not polish their specimens, other than to clean them up a little if dirty or corroded.
Many collectors protect the brass surface by spraying with clear lacquer. Suspend the cartridge with a fine wire around the rim and spray lightly, rotating the cartridge so it is evenly coated. Let any surplus lacquer drip off the bullet nose.
You can protect against the white stuff by cleaning it off as much as possible and then dipping the bullet into a jar of gunstock finish like GB Linspeed. Let dry before returning the round to the collection drawer.-D.A. IRD
Copyright National Rifle Association of America May 1997
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