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45 ACP Case Separation


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For those of you who reload for your Thompson, here is a problem we discovered accidentally last week. I normally do not use reloaded ammunition in the Thompson but made an exception last week with a Savage 28 shooter grade gun. We experienced two stoppages out of 50 or so rounds before realizing what was happening. The brass was once fired Federal with the crimp line (cannelure). Two of the cases separated at the cannelure line and stuck in the chamber. The first one was easily removed with a chamber brush. The second one stuck a live round in the separated ring and jammed approximately 3/8 inch out of battery. The stuck round was fully seated on the bolt face and securely held by the extractor. Considerable effort was required to work open the action. If you reload for your Thompson I would NOT recommend using any brass with a cannelure.

 

This would have been a disaster in the M1A1 with a fixed firing pin!

 

 

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Edited by 1921A
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Disaster indeed! Especially for a Lefty!

 

I have not seen that type of case failure but surely will take the info to heart.

 

Thanks!

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FWIW Federal rifle brass is very, very soft. Their .308 and .223 cases are typically good for 1 or 2 reloads before the primer pocket has expanded to the point where the primer will not seat securely. I've not had a problem with their pistol brass...yet

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Ill try to answer the questions:

 

1. The barrel is original Savage GI in good condition

2. The chamber is smooth and original configuration.

3. We fired approximately 50-75 rds from a clean gun.

4. The brass was once fired Federal.

5. The load was 4.5 grains of Bullseye.

6. The bullets were 230gr FMJ ball.

 

This was a first for me and Ive been shooting Thompsons for nearly 40 years but we normally use Winchester USA factory ammunition.

Edited by 1921A
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How hot was the load??

Has this ever happened with a factory load with this gun??

Is the chamber rough or very over size??

Jim C

Jim - I shoot this gun a lot. Never had anything like this with new factory ammunition including Federal. We shot the new factory Federal ammo through this gun and then I reloaded some of the brass for the pistols. It was a couple of those reloads that separated.

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I had a batch of 223 brass that at one point was too brittle. It would separate at the neck/shoulder junction like clockwork. Junked it and no problems since.

 

I agree with Federal rifle brass being soft. I do not load it. Run their pistol brass no problems.

 

It is also possible the brass coil that became those cases had suspect chemistry, that it wasn't drawn correctly, or the cannulure wasn't applied correctly. The ammunition industry, like all manufacturing, isn't going to be 100 % all the time.

Edited by Dan K
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