Casually picking up a Smith compact magazine it appears to have the exact same problem the P22 and PPK/S .22 zinc pistols have....the mag is just a bit too large to modify. It almost fits into the grip just like the other mags....but it a no go. The PP .22 mag measures 1.060" front to rear. The P22 and PPK/S measure 1.090". The mag well measures close to 1.070". Knocking the P22 down 0.02" or 0.03" proved to require the metal to be made too thin.
The Smith on the other hand measures 1.080". Filing down the spline just a bit and it fit right into the magwell.....as far as it would go...which isn't far because there are some things that need removal. Two punched out tabs along the round barrel need to be ground off. There is also a small punch out that does something but is only in the way for inserting the mag into the frame.
My first mistake was to put the mag on an anvil and tap the little strap back flush. Bad idea. That bent the mag in a bit....don't do this....just cut it off with a Dremel and a small cutting wheel. Leaves a slotted hole...but that is life.
Next simply grind off the two small expanded tabs on the round portion of the mag. In fact, with a medium grit emery belt, neatly round off the entire front and a portion of the side of the mag barrel while you are at it. Spline cut down a bit, front rolled neatly over the belt and the mag should now fit perfectly into the magwell. Going from 1.080" to 1.070" is a whole lot easier. Plenty of metal left.
Of course the follower fits, as does the spring, spring base and bumper. The bumper is too long in the nose and will be ugly even if ground off but it does fit everything else on the mag. The spring base fits neatly, has a long leg that stabilizes the lower portion of the spring. At this point only four things remain. Insert a gutted mag into your pistol, slide locked open. Mark how much of the front of the left ear needs to be cut off to clear the ejector leg. About half. And while you are at it, cut it down, then cut across the front of the mag so it won't run into the bottom of the feed ramp. 1/8" should do it. You can at this point grind a slant on the nose of the mag to aid the catch slipping over the rim if you like. Just leave enough steel so that it won't bend in....or insert your mags with the button pressed in. Easier on everything.
While you are doing this you need to stick the empty mag body into the pistol until the rear cutout for the breech rail is just a tiny bit taller than the rear of the frame. Neatly mark the rear of the mag right at the base of the frame. Cut a small slot across the rear of the mag and then neatly punch the lower portion of the mag out. This bump out will now stop over insertion. Cut it too high? No problem, just neatly file off the top of knock out to let the mag insert a little higher.
I'll put up a picture to show where the cutout for the mag catch goes. Walther has the shape that they do for a reason. It isn't critical, but a thin slot that lets the nose only on the catch, catch....isn't good enough. The bottom of the catch slants down so you need a hole there large enough for the mag not to interfere with the lower portion of the catch.
Almost there. The follower is going to have to be modified if you want the hold open function to work. Like the P22 there is a ridge running down the center of the follower and that ridge isn't wide enough to engage the stop arm. So, you have to grind some of it off. Polymer, so pretty easy. Don't cut it all the way down like I did on the P22 or it will engage the ejector with one round still in the mag. Might as well shoot all ten rounds. Grind off all of the follower flat except about the last 1/8". Then, re-
slant the rear rail. Take a close look at a stock follower and how it fits the mag. There is a slight chamfer at each rear corner and you will have to notch the rear edges of the round, front portion of the follower. It appears to me that the rear rails and front lips both stop upward movement of the part.
You will not be able to use the polymer follower pull down button. It is not in a recessed portion of the mag body....so, it isn't going to fit under the frame. A regular PP pull down is very thin and would not work either except that it is located in a pressed in area of the mag. To fit a similar pull down button you will have to cut a long slot which will weaken the mag and I don't think is worth the effort. After a couple of rounds are inserted you can stick something in the follower hole and pull the thing down as you drop rounds into place. Easier than some of these tiny button levers anyway.
Clean everything well, load and test fire. Mine ran 100% except the follower locked the slide open with one round still in the mag. So now I will have to cut the left shoulder of the round portion of the follower off just a bit. It would have been better to have known this beforehand.....because the shorter the follower the worse it wants to bind. This one wasn't ruined but the next one will be better. Since I have three of these mags and no crooked shooting compact....I'm converting them all to PP .22 mags.
Still looking for that Bersa mag to see if it isn't more or less a drop in with very few mods. Pictures soon. 1917