Reader Forum

Removing Revolver Endshake I recently acquired a Smith & Wesson Model 28 with recessed chambers. The cylinder appeared to have quite a bit of fore-and-aft play, so I measured the headspace and barrel/cylinder gap with feeler gauges. With a deprimed .357 Magnum case in the chamber, I measured headspace of .013 inch and a barrel/cylinder gap of .007 inch. Question 1: What should these measurements be? Does the gun need to have its endshake adjusted?

Question 2: There appear to be two ways to accomplish endshake adjustment. Method one swages the cylinder arbor with a tool that resembles a tubing cutter followed by truing/trimming to length with a piloted cutter. Method two first trues the end of the arbor with a piloted cutter and then adds shims to bring the endshake within tolerance. Is one method to be preferred over the other? If so, which?

Assuming no barrel/cylinder-alignment problem is present, if there is leading build-up at the rear of the barrel, the gauge may have to be increased and/or the ammunition changed. The rear gauge (headspace) is factory set according to caliber. Calibers .38, .357, .41 and .44 are specified at .060 to .068 inch; .22 Magnum at .004 to .008 inch; .45 ACP at .090 to .094 inch; .45 Long Colt at .060 to .068 inch; and .38 or .357 with cylinder counter bore at .012 to .018 inch.

Some of America’s top revolversmiths are in agreement that tolerances should be based on how the gun is used. For example, a PPC revolver should be gapped at .005 to .006 with headspace of endshake of .0005 to .0010 inch. In the same order, the consensus for a duty or personal-defense gun is .005 to .006, .004 to .005, and .001 to .0015 inch; for a silhouette gun, the measurements are .0015 to .0025, .003 to .004, and .000 to .0010 inch; for sporting use, .0015 to .0025, .003 to .004, and .0005 to .0010 inch.

For IPSC competition, the numbers are .0025 to .0035, .001" to .002, and .0005 to .0010 inch. Stretching the yoke after its barrel has been supported with a metal rod or hardwood dowel can be done with a tubing cutter, but not one directly off the shelf. It must be modified by removing the cutter wheel and grinding the wheel to approximately 3/32-inch wide, then stoning it to remove any burrs. Smooth and free spinning is the word.

The yoke is given more room to turn in the tool by filing down the cutter frame on the left side by 1/ 32 inch and the rollers, if grooved, should be reversed to provide more bearing surface on the end of the yoke barrel. A second method of stretching a supported yoke barrel is by peening. The yoke is removed from the cylinder. Work on a hard, true surface. Use your hammer to peen all around about 1/32 inch from the barrel end of the yoke. Peen too much and you will cause cylinder bind.

If you do, you can reduce the peened area a bit by rolling the yoke on a fine file. Follow this by doing the same to it on a perfectly square Arkansas stone. By far the simplest method, often preferred when time is a critical factor, is the use of endshake bearings. These are available from Brownells in several thicknesses and are revolver specific. Whitney Wolverine Takedown At a recent gun show, I purchased one of the new Whitney Wolverines.

It had been fired some so, once I got it home, the first order of business was to field strip and thoroughly clean it. However, even following the instructhe barrel jammed about halfout. With the hammer at full, it presses against the underside of the barrel, wedging it in place. Because of a small piece which indexes to the top of the barrel and which came loose while I was fiddling with the gun, I haven’t been able to reassemble it, either.

I probably could get that piece back in place with some needle-nose pliers, but I haven’t had much time to work on the gun (which, fortunately, also means I haven’t had time to cause any damage). However, I’d like to get it back together and do some shooting. I would appreciate any advice you might have before resuming my attempts. Perhaps the previous owner messed things up with an ill-informed stab at a takedown job.

We suspect the loose part you mention is the ejector, but are puzzled since it’s pressed into the barrel and doesn’t come out easily. We did a full article on the new Whitney in the March 06 issue. With the exception of mistakenly referring to University of Washington footballers as "Wolverines" instead of "Huskies," the article is an accurate and complete guide to proper disassembly and reassembly. It should serve to resolve your problems.

HK Questions Do you or anyone you know have information on working the HK USP and Compact, especially trigger jobs, et cetera? Thank you for your help. John Starling Farmville, North Carolina The USP, especially the Compact, is more of a duty weapon than anything else. It’s purpose is close-in self-defense. Takedown and reassembly for the pistol appear in Gun Digest’ s book of disassembly/reassembly dedicated to pistols.

We don’t know what you mean by "et cetera," but if you’re thinking of a target trigger job, the USP would not be a good candidate. In cases where USP owners, including law enforcement, find the gun’s trigger pull intolerable, the offending pistols are normally returned to the factory or handed over to a crackerjack gunsmith. In those hands, the gun is torn completely down and given a detailed polishing to reduce or eliminate internal friction.

This includes the sides of all trigger-system components, their related pins, and any points of contact

where rubbing has occurred between those components and the frame or slide. There may be a reduced-power spring kit that would still allow the gun to function as designed. We haven’t scouted the aftermarket to find one, but Wolff Springs would be a good place to start Add to that a scan of the Brownells catalog. We strongly recommend that no cutting of OEM springs be done in search of a lighter pull.

Do-It-Yourself Light Mount I live in a rural area of Mississippi about 100 miles north of the Gulf Coast and after Hurricane Katrina in 2005 we were without power for 13 days. (We were among the lucky ones; we still had a home.) As stories of looting and violence were circulating and law enforcement and emergency services were stretched thin, people were on edge and neighbors came together to watch out for each other. (Call it the ultimate neighborhoodwatch program.) My gun-repair shop is attached to my home, which made it easier for me to keep an eye on both my home and my business at the same time.

My closest neighbor and I started taking turns staying up at night and keeping watch over both of our properties. We taped flashlights to our long guns to make them more efficient during our nightly vigils. Fortunately no one decided to bother us during this time, so we didn’t have to test how well our hastily devised night weapons worked with their taped-on lights.

After all of this was over and our power was restored, I took a closer look at my AR-15 and the light I had taped to it, and decided that I needed to improve upon it. Since my shop was by necessity closed for two weeks and the cost of gas and supplies had skyrocketed, buying one of the quality lights on the market was a no-go for me. So I started looking for a less expensive alternative. I went through my shop to see what I had to accomplish the job.

The collection of parts I assembled included a Weaver #45 scope-mount base, an off-brand Weaver-style scope ring, a Brinkman Maxfire flashlight with a momentary onoff switch on the tailcap (it uses lithium batteries and the beam is blinding), and a couple of screws and nuts from the junk bin. The first step was to mount the light in the scope ring and then secure the ring to the scope base.

Using masking tape to hold the contraption indifferent places, I next decided on where to position the light on the rifle’s forearm. Obviously, the best position for the light will vary from shooter to shooter. The best position for me was on the upper forearm on the left side. With the lights tailcap switch placed 7 inches or so from the front of the rifle’s carry handle, I only had to raise my left thumb from my normal shooting position to activate the light switch.

Using masking tape, I then marked the forearm around the scope base to keep from losing my place and then removed the mount and light. After separating the ring from the base, I drilled and countersunk the screw holes on the scope base for the machine screws I had selected to fit. Then I removed the upper forearm, and using a Dremel tool and a small stone, I cut a groove on the underside of the scope base to fit over the rib on the forearm to allow the base to fit flush.

From that point, it was a simple matter of marking and drilling screw holes through the forearm and heat shield and attaching the base with the screws and nuts. (If you try this, be careful that the placement of the mount doesn’t allow the screws to contact the fragile gas tube.) The ring with light can now be attached or removed in seconds as needed thanks to the handy thumbscrew on the ring.

While this setup is not as fancy as the some of the aftermarket mounts, it Technical Assistance Hotline To access AGA’s Technical-Assistance Hotline, call between 1 and 3 p.m. ET, Monday, Wednesday, and Friday once at all other times, you can send an email to Chick Blood, Technical Editor, at certainly gets the job done. In addition to being inexpensive, another advantage of this type of mount over some of the commercial ones is there are no wires and pressure switches that must be taped or glued to the gun.

Daniel Robbins Mt. Olive, Mississippi AMT Backup Info I recently purchased a used AMT Backup in .45 ACP, and was wondering if there is any technical data available. It’s double-action-only, all stainless, and in very good shape. Have there been any articles in American Gunsmith on this particular handgun? If so, could you give me the issue number and date of printing. I’m especially interested in an exploded view and field stripping instructions.

No articles, but you can go to and click on "Pistols." A drop-down menu will ask you for "Manufacturer," under which you’ll select "AMT." Three guns will be shown, and the Backup is among them. A PDF version of the owner’s manual will cost you $1.49, charged on-line to your credit card. Chamber/Forcing Cone Data I’m looking for chamber and forcingcone dimensions for 12-,16-, 20-, 28-, and .410-gauge shotguns. I am considering lengthening the forcing cone on a 16-gauge Citori.

I was wondering if I need to take a forcing cone to the same size as the chamber, or if I can leave it .010 to .020 small if it is for one shell length only (like a 16 or 28 gauge). I can understand the need to have it at the chamber diameter if it is a 3- or 3-1/2-inch chamber, since most are designed to take a

(continued from previous page) shorter shell. In the case of a 16 gauge, there is one length, so I think if it’s a little small the opening of the hull would prevent the wad from hitting a .010 shoulder. Is this correct? Where can I get these dimensions and other information on this topic? Where can I get the reamers for this besides Brownells? I would like to get one with an interchangeable pilot to match the bores and keep it in alignment if possible.

I know the Browning Citori does not have chrome-lined bores, but I may do another shotgun that does. Should I get a carbide reamer for both? Brownells states that the carbide reamers are not recommended except for chrome-lined bores, but I have used carbide reamers, drills, and endmills for other machining. Would performing this operation on a gas-operated gun such as the 1100 or 11/87 affect the cycling, since it would theoretically lessen recoil? Any information would be helpful.

Let’s start with the definition of a forcing cone: The front part or "throat" of the chamber where chamber diameter is brought down to bore diameter. It is believed this aids the passage of shot into the barrel. Whether along or short forcing cone is better is a mater of some disagreement, but it seems everyone who makes barrels has his own set of rules on that length. For this discussion, a rule of thumb for throats is 7/16 to 11/16 inch. Forcing cones can be of a shallow or steep angle.

Steeper angles tend to deform pellets more than shallower angles do, and deformed pellets fly more erratically and thus shot patterns tend to spread. We have read of skeet shooters from days past who favored very soft lead or even squareshot loads to improve their "kill" rates. (Square shot is no longer permitted in competition.) Take note: The crimp of the shotshell unrolls as the gun is fired.

The chamber must have sufficient length to accommodate this "blow-out" condition, and some 2-3/4-inch shells do not reach 2-3/4 inches. This raises pressures, deforms shot, and affects patterns. Therefore, the forcing cone must never constrict the full opening of the hull. Chamber specifications are available from S. A. A. M. I. Newtown, CT 06470) and Clymer Manufacturing is a good source for reamers, although we think the kind Brownells sells are made by Clymer.

Broken Drill Removal I have broken a #31 drill bit in a Mauser receiver. Before drilling, the locations of the 6-48 screws were marked. (The top of the receiver was ground a few thousands until it was easily marked with a center punch.) The hole was started with a center drill, then deepened with the #31 drill bit. This hole is in the rear of the receiver, and I intended to drill through. I suspect that when the drill bit encountered the case-hardened interior of the receiver, it snubbed up and broke off.

The drill bit is part of the Brownells tap & drill kit #2, which list the drill-bit composition as HSS. Please advise what you think is the best approach for getting me out of this embarrassing dilemma. I do not have access to EDM. Thank you. A 1/8-inch bottom-cutting carbide endmill set up dead rigid in a milling machine (Bridgeport or equal) will ream out the drill stub. The result will be .005 inch over for a 6-48-diameter screw.

There are oversized 6-48s available, or you could move up to 8-40, then redrill and tap the hole using generous amounts of cutting oil. Too bad there’s no machine shop nearby with EDM capability. Such a shop could make your problem easier to solve. Parts Sources I have two weapons that I can’t locate parts sources for. The first is a Benelli B76, 9mm semi-auto handgun. The second is a Norinco .22 ATV (a lookalike of the Browning .22 Auto). The Norinco has a broken extractor. Cana Browning extractor be substituted?

I would appreciate any help you can provide. Our former source for Benelli pistol parts is apparently out of business, but try Gun Parts Corp. and Bob’s Gun Shop Regarding the rifle, it all depends on how close Norinco came to swiping the Browning design. If they came close, a Browning extractor could probably be used with minor fitting. It’s worth a try anyway, since the part isn’t expensive. If you run across an importer for the Norinco (possibly in the owner’s manual), let us know.