Auto Ordnance M1a1 (WW2) has two Problems-Need advice

[Grease Gunner]

Hello All:

Have a Auto Ordnance M1 That has two problems.Sold it recently after shooting thru it one Magazine to make sure it functioned

On last round, Bolt it not locking back.When mag is released bolt goes forward. Is that a magazine issue?

other issue is that when the shooter releases the trigger, it can fire two additional shots. Does a part need replacing?Or might it be the ammo he used

Answers are appreciated

Thanks

Grease Gunner

 

[68coupe]

There's an issue with the mag or trip lever. There is a tab on the back of the mag that should "trip" the lever, locking the bolt back. The other issue is likely a weak, broken, or gummed up sear spring. I have experienced both issues.

V/R, Karl, 68coupe

[Motorcar]

Sounds like trash, carbon, brass, dirt and debris in the trigger frame parts and springs. Yes it could be worn parts, but before I started swapping things out I would take that lower grip off and hose it out with a good gun parts cleaner and blow it out with compressed air. Then oil it up good. Chances are that will clear things up. Only after that would I start looking at the finite small parts and springs if it exhibits the same problem.

[dsp]

Was talking to reconbob once upon a time and he told me that when a barrel has enough rounds thru it, gas pressure will "blow by" or leak around the bullet in the barrel and not provide enough recoil pressure to fully open bolt far enough to catch on the sear.  Bob told he had worked on a gun range rental m1 thompson with meticulous round count records and it had an unbelievable number of rounds thru the gun.  He said all components were in excellent condition other than the barrel being shot out.  If you could get someone to take super slow motion video with a latest generation smartphone, you may find that bolt is not recoiling all the way back.

[dsp]

Note that there are two "sears" that will catch and hold back the bolt.  One is the main sear that holds the bolt at fully retracted position.  The other is sort of a safety catch/sear that will hold back the bolt if it short strokes.  This safety catch will hold the bolt open at about 3/4" from fully retracted position.  If recoil pressure doesn't push bolt back to fully retracted position, barrel could be the problem.  The hotter the barrel gets, the worse the blow by will be.  M1 tommy guns are made to fire fairly low velocity ammo.  If problems are occurring with low velocity ammunition, you could see if problem goes away with higher velocity (higher pressure) ammo.  If it goes away I would assume it's the barrel.

[reconbob]

   If the gun fires one or two rounds when you let off the trigger, I’d say the bolt is not recoiling far enough back to be held by the sear. The bolt not back on last shot could also be short recoil or the trip/mag follower/disconnector malfunction.

   I consider S&B and IMI to be the hottest .45 ACP ammo. If the gun works with that ammo, the barrel is on its way to being shot out.

  One test you can do is fire one round with the gun on semi. Pull the trigger and hold it tight - the bolt should recoil and be held by the sear.

   The gun cleaner and air gun is a bad idea. There is no clearance for dirt/fouling to get blown out of the pocket in the trigger frame. The sear and sear lever are right up against the sides of the pocket, and the bottom rear of the pocket has no openings. The sear, sear lever, and trigger springs are in upside down blind holes that all the crud is going to get blown into, not out of. The disconnector spring is in a blind hole. 

Bob

 

[Motorcar]

13 hours ago, reconbob said:

The gun cleaner and air gun is a bad idea.

Hosing it out and oiling it up to see if the problem resolved itself was a quick way to diagnose an issue, certainly not a permanent one.

I would think in the winter and spring of 1945 generous amounts of lube were dumped in the trigger frames of M1/M1A1s that had thousands of rounds shoved through them, without the benefit of a sterile armorer's lab coat to get all the pockets clean. We have no way of knowing the last time or if ever this trigger group had a full disassembly and cleaning, so I responded with a way to start the process of diagnosis. Total time invested by employee in charge....5 minutes?

Mine is 84 years old and running fine.

[full auto 45]

Take the gun apart, put the lower in an ultrasonic cleaner with Simple Green Cleaner let it soak for about 5 or 10, then put it on vibrate for 5 minutes or longer and be surprised at how much crap will come out. My M1 had a similar condition of misfiring. Cleaned it, oiled the hell out of it and it works great.

[Outsider]

When  I got my M1A1 I literately cleaned chunks out of it because it was not cleaned. Ran like a top after cleaning. 

[Doug Quaid]

wouldn't a complete disassembly, thorough cleaning, and new spring kit be in order?

that gun might have 70 year old springs in it