Tuesday, December 08, 2009

Rimfire Magazines - Part 1

One of the most common problems with rimfire semi-automatic pistols is failure to feed. Back when the rimfire .22 cartridges were designed, semi-automatic rimfire pistols weren’t around, so the cartridge rim wasn’t a problem. When you stack ten of them up on top of each other in a magazine, though, the rims keep the cartridges from lying flat and parallel to each other. By slanting the magazine, at least the rims aren’t up against each other, but are staggered one in front of the other, making things a bit better, but still far from ideal.

Rimfire failure to feed problems can be caused by one or even several different things, so solving the problem often isn’t easy. One of the possibilities is a problem with the magazine itself. Before doing anything else, disassemble and thoroughly clean the magazine. Most rimrire pistol magazines can be disassembled for cleaning.

A typical rimfire semi-automatic pistol magazine. This one's for a Smith & Wesson Model 22A. Note the round cutout at the bottom of the slot.

To disassemble the magazine, I use a thin piece of wood, or whatever else might be handy, to compress the follower spring and to hold the follower all the way to the bottom of the magazine. This will allow you to grasp the follower pin with a pair of pliers and pull it out of the follower through the larger round hole at the bottom of the magazine slot. The follower pin has a small flange on it that keeps it from coming out, being kept into place by the sides of the magazine slot. Once you have removed the follower pin you can let the follower back up to the top of the magazine body. On some magazines the follower is thin enough that it can now be taken out through the top of the magazine, along with the follower spring.

"Special Factory Service Tool" being used to hold the follower at the extreme bottom of the magazine.

Other brands of magazines may have a removable floor plate, or magazine bottom. Often the follower spring is also the retainer for the floor plate. On the Smith & Wesson magazines used of the Model 22A, for example, slip a small rod, punch, drill bit, nail, or whatever’s at hand through the slots on the side of the magazine and pull the follower spring away from the bottom of the magazine a bit. Once you have done so, the plastic bottom piece will slide rearward off the magazine.

Compressing the follower spring to allow removal of the floor plate. The floor plate is almost removed.

Now you can clean everything and inspect the parts for any obvious burrs or defects. A little bit of smoothing and polishing with some very fine “Wet-or-dry” sandpaper is not a bad idea while you’re here. After everything looks good, thoroughly clean everything, lubricate the pieces, and put it back together. From my experience, the tension of the magazine follower spring is not particularly critical. I’ve seen a wide variation in spring tensions all work fine, as long as the magazine and follower are free and smooth from top to bottom of their travel.

The fully disassembled magazine.

There are a lot of things you can use for lubricating a rimfire magazine. A dry lubricant such as CRC 5-56 Silicone or LPS dry lubricant work well, particularly in a dustier environment where oil tends to attract and accumulate dust. I use Tri-Flow, a spray oil with Teflon, most of the time. Any oily lubricant should be used sparingly, though. Brownell’s also has excellent oil under the Brownell’s brand name.

Model 22A magazine catch holes, a source of mis-feeding problems.

Speaking of 22A magazines, they have a “Designed-In” feeding problem that affects some types of ammunition and not others. There are two small square holes on the front of the magazine about half way down. These are for the magazine retention catch. Depending on the shape of the nose of the bullet, it can snag in one of these holes and the rounds won’t move up in the magazine as the top one is removed. The somewhat “squared-off” hollow points seem to be the worst, and fairly narrow round-nosed bullets like CCI Standard Velocity seem to feed the best. On later production of the S&W 22A magazines the factory has dimpled-in the spot between the two square holes to reduce or eliminate this problem. In most cases it seems to have solved the problem. The magazine pictured has a thin aluminum liner glued to the inside front of the magazine. It never hangs up, regardless of bullet shape. I’ve also experimented with a very thin stainless steel liner, and it also works well.

Once you have your magazines all cleaned up and lubricated, put a mark or a number on each one so you can tell them apart. Make sure your pistol is also nice and clean and properly lubricated too, while you're at it. Grab a brick of .22 ammo and head out to the range. For testing purposes I'd go with something like Federal Bulk, or CCI Blazers, as they should both run well in just about any rimfire semi-auto pistol.

End of Part 1



At Tuesday, December 15, 2009 7:25:00 PM, Blogger Firehand said...

I mostly use Eezox for things like magazines: takes a while to dry, but then it doesn't attract dust and seems to last quite well.

And it's a hell of a protectant against rust


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