What Would Cause This? (AR 15 Issue)

[Batteriesnare]

Took my AR to the range today (Stag Arms M4gery, 1/9 twist barrel marked 5.56) and I had a couple of significant ammo failures. The rifle had been completely stripped and detail cleaned last week and had not been shot since.

I was firing Winchester Q3131A that I bought from a fellow board member that appeared to be in good condition. After a few rounds I had a jam where the bolt would not close completely so I dropped the mag, cleared the rifle, and pulled back on the charging handle, locking the bolt in the rear most position. I then noticed that there were little metal star shaped objects just before the chamber. I dumped them into my hands and they appeared to be the innards of a primer. I then searched the brass on the ground, and sure enough, two empty cases were primerless. I immediately stripped the rifle looking for damage, and couldn't find any. I then reassembled and continued firing using UMC .223 without incident. I couldn't find any stress marks on the spent UMC cases.

What would cause this to happen? Was it just a bad piece of ammo, or should I avoid the rest of the ammo I purchased (500 rounds).

Thanks!

[Elhuero]

sounds like bad ammo to me, if it shot fine with a different brand.

occam's razor

if you're adventurous, pull out a few randoms of the winchester and try them.

[Richard K]

There was a post on the "other forum" about a bad batch of that ammo which caused high pressures.

[sniper7]

sounds like high pressure blowing the primers out. might be a primer issue as well. not sure. i dont think i would risk damage to your bolt. get the lot number and call winchester. hopefully you have the cases and the remaining ammo. take pictures. this is another reason i dont use winchester ammo or their components. ill post a link to my reloading data i did comparing hornady and winchester bullets. you would be amazed at the difference. glad you and your gun are all right

[low drag]

I know of 2 things that cause primers to pop out.

Over pressure ammo and out of spec primer pockets in the brass.

If you still have the brass can you measure the inside diameter of the primer pocket? The out of spec brass I had measured .177 while the stuff that worked fine measured .175

[theGinsue]

Are you certain that this ammo is factory and not reloads?

Something just doesn't sound quite right.

[bczandm]

Are you certain that this ammo is factory and not reloads?

Something just doesn't sound quite right.

I'ved used Q3131 and Q3131A for years and never had a problem. It's my favorite ammo. DON"T shoot any more ammo, from any mfg before the rifle is checked by someone who knows what they are doing. You and the rifle could be seriously harmed.

Have you shot the rifle before, without problems? It sounds like too high of pressure and I'd bet it's an ammo problem, but without knowing your rifle I'd get it check out. Something as simple as hot 5.56 in a .223 chamber can cause this (voice of experience).

In any event, on problems like these I like to error on the side of caution to prevent any serious injuries.
Bob

[MuzzleFlash]

Wonder if the firing pin could have pierced the primers during setback? Have you examined the firing pin and verified that it and the channel it lives in are free from grunge and crud?

[Batteriesnare]

Thanks all for the responses. Something just crashed outside the apartment so I'm awake.

A little more on the ammo:

I'm pretty sure its factory new. When I purchased it, it came in 20 round Winchester sealed boxes (just like the little white 5.56 boxes you find at Walmart.) The boxes are from batch SC62 and the blown cases are stamped from 2001. All individual boxes were factory sealed and in excellent condition.

Prior to purchase, I inquired as to the age, and the seller told me there were of older manufacture (new, not recent) and had been stored in water tight ammo cans with silicon moisture packs. I don't know if any of this changes anything, but I thought it may help. I'll see if I can track down a good digital camera in the next couple of days to take pics, all I have now is my webcam.

Muzzleflash:

I didn't notice anything strange on the bolt or firing pin after the incident. I'll do a more complete search tomorrow. Prior to firing it, I had completely stripped the bolt, cleaned the snot out of it, let it air dry for a day, properly lubed it and reassembled it, so there should not have been anything in the way. I'll take another look and post my findings tomorrow (today, whatever).



Thank you all again!

[sniper7]

If it is factory ammo like the guy claimed then I would call winchester with the lot number and also do a quick google search to see if anyone has had problems with that particular lot. If so that would make a good case against winchester to get them to send you some new ammo.