LC Brass Case Failure 1st Firing

[evanst78]

Has anyone had a piece of lake city brass have a case failure on its first firing? I went to the range on Sunday with my cousin who was shooting a lot of 62gr green tip .556 out of his AR. About a half hour into shooting I noticed one of the cases on the ground had completely separated from the head. The gun didn't do anything odd and the only indication there was and issue was the case on the ground. He continued shooting a few more rounds (maybe 10) and the gun jammed. I looked down and there was another case head on the ground. This time the rest of the casing was stuck in the chamber. That stopped us from shooting that gun for the day. I never heard of a case failure like this on the first firing before. Is this common? The rounds were not reloaded to my knowledge. They were purchased at a gun show in PA from a guy who sells alot of surplus ammo and still had the orignal crimped primers with the primer sealer. But they were oddly packaged in heavy heat sealed clear bags.

 

[223ai]

Re: LC Brass Case Failure 1st Firing

I had a rifle that did that to brass, exactly. The chamber was cut incorrectly, resulting in incorrect headspacing. Also, I'd bet money that those are reloads and that they were fired from a loose chamber and resized too much.

 

[KYpatriot]

Re: LC Brass Case Failure 1st Firing

Is this a new AR? It could have a long/improperly headspaced chamber. Or that brass is too short. Pull some bullets and measure the brass.

 

[Oneteam]

Re: LC Brass Case Failure 1st Firing

+2 on the headspace. It could have been a weak case or a timing issue. If the case was still "swollen" in the chamber from firing and the extractor was already pulling it out, that could happen, but very unlikely.

 

[1lnbrdg]

Re: LC Brass Case Failure 1st Firing

If it was machinegun fired brass before reloading, this is a usual result. Machineguns are normally headspaced longer causing the results you are seeing.

It can happen in unfired cases but not usually on the 1st firing (re: see maching gun statement above).

Just to be sure, it wouldn't hurt to measure a fired case against an unfired case to see how much difference there is in headspace.

 

[evanst78]

Re: LC Brass Case Failure 1st Firing

It is a newer AR. It has probably fired over 1500 rds though. This is the first time we noticed this issue. I am thinking after reading your replies that this brass was improperly sized. I will have to see if I can get any off of my cousin to measure. I koow he only had a few left in the lot. He might have tossed them. We'll have to see if we have any case failures in the future with other ammo which might indicate an improperly cut chamber.

 

[Apex Motorsports]

Re: LC Brass Case Failure 1st Firing

The M249 has longer head space field gauge than the M16/Ar15 platforms. Also I would venture to say that your head spacing may be less than optimal. Example, for bolt rifles in 223/ 5.56 your usually minimum head space to +0.002, for auto loaders (read ar15) depending on who you ask it's min +0.002-0.004. Longer than that and case head separation becomes an issue. Sammi allows for +0.007 if I recall.

Hope this helps

 

[Edo1]

Re: LC Brass Case Failure 1st Firing

Can you show us a picture of the markings on the base?