Unusual Malfunction
 

My son is an LEO- While adjusting a new optic, his M4 started have a failure to cycle. He took it to his armorer who discovered a piece of primer in the gas tube. The armorer said he had never seen anything like it in 30 years. The armorer thought it was the Winchester ammo he was using...

Never saw that in the M4 but have in the SR25 shooting Winchester ammo.

The anvil?

In the end of the gas tube that goes into the Gas Key?

Was he shooting 5.56 in a .223 chamber and popped the primer?

A piece of the primer, not the whole thing, ended up in the gas tube, I don't know how far, but the armorer saw it when he shined a light in to the tube. Next time I talk to him, I will get more details...

Guys:

Happened to me with a JP upper and some handloads. Can't remember the brand of primer. The primer blew and got stuck in the gas key. Had to totally replace the gas key.

I can't begin to imagine the probability of that happening as the primer barely fits into that thing.

Gene

I spoke to my son. The piece of the primer was in the gas key, all the way to the back of it.

I have seen primer parts only once in the gas key.

Just witnessed this week a primer wedged in between the bolt carrier and cam pin, was a bitch to remove the carrier from the weapon.

I heard about primers comming out and locking up M60s back in the Late 80s to early 90s. That put my "Reloading Operation" of .308 on hold.

I have personally seen 5 documented cases of this happening. In every single it was due to the chamber being non 5.56 and the primer blew back into the weapon during the cycle of operation.

The weapons that I know that were involved were Bushmaster carbines and 1 DPMS.

Loose primers are generally a pressure or overworked brass indicator.

The chamber issue can cause it as well, via pressure spikes.

Do not shoot 5.56x45 in .223 chambers.

TR

Iraqgunz:

You have only seen five cases of blown primers in AR's? He, he, he. I have seen guys shoot rapid fire strings and blow several primers in one string. And it wasn't because they were shooting 5.56 through .223 chambers and jammed the bullets into the rifling, thus causing a pressure spike.

It was because they thought they were getting over by getting another twenty fps out of a already too hot load, fired on a more than average hot day, after their ammo sat in the sun for a few hours and cooked.

I don't take blown primers as easily as some guys. It means the guy either made a mistake in his handloading or took an unnecessary risk to win a match.

That said, I can't recall one experience with Lake City 5.56 blowing a primer in an issued service rifle or carbine. Crimped primers do work.

Gene

No, I mean specifically 5 cases of primers that have blown back into the upper and getting into the carrier key. In all the cases that I examined the ammo was either M855 or M193. All the chambers that I checked were in fact not up to 5.56 specs.

OK -- now I am curious.

What process did you use to inspect the chambers and how are you sure the chamber was the problem and not the gas system / timing?

One of the gunsmiths in my neck of the woods had posted the following reply regarding this same issue. I have not used him as a 'smith before, but he gets some good reviews from the locals. Here was his reply on another forum "marylandshooters.com":