Any Beretta 21A Experts? Having Function Issues

[Glocktogo]

Ok, I have a new to me Beretta 21A. The barrel is threaded for a can. It functions flawlessly when I shoot it bare, but about once per magazine it will double with the can on. I've completely disassembled, cleaned and lubed it. Everything appears to be working fine outwardly. When it doubles, it's so fast that it's almost hard to tell whether it was one shot or two (but it's two). I've worked the slide and it doesn't seem capable of feeding another round from the mag without going back far enough for the sear to catch the hammer. The action bars are obviously stout, but move smoothly and freely. The mainspring seems about what I've encountered with other 21A's I've shot. With the trigger held back, I can't get the hammer to fall while manually working the slide and the single action feels like there's plenty of sear engagement. It's happening in the middle of the mag, not 1st round, so it's not a DA/SA issue.

Any thoughts? I seem to be chasing my tail here and I'm not too keen on changing spring rates without a couple of extra spring sets on hand in case it doesn't work out.

 

[Rob72]

I've had a 21a and (now) Taurus' copy, the PT-22, and have worked over a few others. My best guess, based on what you describe:

You say it only does this with a can on. The can can't effect your trigger group(sear being the other obvious possibility) so I'm going to suggest a worn/undersized barrel lock pin. If the barrel is being pulled down by the extra muzzle weight, out of square to the breech face, and you get that in conjunction with a primer on the "thick" side, it does a slam fire.

Getting pretty detailed for a 21a, but if this does look to be the case, you/your smith could ream the chamber & rim seat just a thousandth or two. You could replace the barrel locking lug, but without knowing how much gap may be related to wear, vs. factory tolerance stacking, that may or may not fix the problem. Don't recall offhand how much a new lever is, but for under $20, I'd probably try that first.

As far as diagnostics, for this one you'd just have to fire and pick up individual pieces of brass until you got a double, then use a rim thickness gauge to compare.

Could be something a whole lot simpler, I suppose, but from what you say, that's my thinking...

 

[Glocktogo]

I've had a 21a and (now) Taurus' copy, the PT-22, and have worked over a few others. My best guess, based on what you describe:

You say it only does this with a can on. The can can't effect your trigger group(sear being the other obvious possibility) so I'm going to suggest a worn/undersized barrel lock pin. If the barrel is being pulled down by the extra muzzle weight, out of square to the breech face, and you get that in conjunction with a primer on the "thick" side, it does a slam fire.

Getting pretty detailed for a 21a, but if this does look to be the case, you/your smith could ream the chamber & rim seat just a thousandth or two. You could replace the barrel locking lug, but without knowing how much gap may be related to wear, vs. factory tolerance stacking, that may or may not fix the problem. Don't recall offhand how much a new lever is, but for under $20, I'd probably try that first.

As far as diagnostics, for this one you'd just have to fire and pick up individual pieces of brass until you got a double, then use a rim thickness gauge to compare.

Could be something a whole lot simpler, I suppose, but from what you say, that's my thinking...

Thanks for the info! I had someone else suggest reaming the chamber & throat on another board. I'm thinking it's a slamfire rather than a bumpfire or other cause. This particular specimen hits dead on at 7 yards and shoots very tight groups if I take my time, so I'm gonna do what's necessary to make it work.

 

[Rob72]

I would sort my ammo by rim thickness first, then, and see how the varying groups function. Ream only to the depth of difference (and it really should be pretty minute), otherwise you'll have a whole bunch of rounds that are seated too deeply to be reliably ignited...