Strange AR jam

[fwestrom]

The other day I was firing my Rock River AR, which has now seen 60 rounds, and somewhere around number 45, I had what I can only describe as a unique jam.

After firing, the spent casing cleared the chamber and placed itself half-way back into the magazine (imagine pushing a round half way out of the magazine, so that the follower and other rounds are still displaced). The bolt locked in the open position, as thought the magazine were empty.

It took me a minute to realize what I was looking at, and all I could really do was laugh a little.

I haven't done much looking, but I've never seen or heard of this kind of jam in an AR before. Anyone ever have a similar jam?

[gold cup abuser]

Few things to go over...

Make sure that you are loading the magazine properly and that the bottom of the round is all the way to the back of the magazine.

Clean the magazine and do not lubricate the insides.

Look at the top of the magazine and inspect the feed lip area. If they are bulging, not even or look wide then its time to replace the magazine.

From your malfunction it sounds like that magazine is goiing bad, the feed lips are more than likely the culprit here.

Check that magazine against a know good magazine and give it a good going over. If the feed lips are bad then discard that magazine ASAP.


Good luck and hope this helps

[Asmodeus6]

Could have been an odd bounce. But could be the sign of worse things to come. I think I know what you are describing and I would probably take a close look at the ejector. If you still have that piece of brass / case etc w/e see if there was any kind of deformation - and that it was clearly struck out by the ejector.

I'm thinking maybe it pulled the rim off, or the extractor is weak, let go before the ejector bumped it out - it dropped back onto the magazine the forward running bolt slammed it half into the mag, and then rebounded onto the bolt catch.

That would be my guess. So check for a weak/worn extractor, or case deformation.


The magazine would have most likely caused a FEED issue, not an ejection issue. (Like if what you described what you did but it was not a spent round - but a new one in the same position. I would +100 Gold Cups synopsis.)

[devinsdad]

Ditch the mag.

[fwestrom]

Originally Posted by Asmodeus6

Could have been an odd bounce. But could be the sign of worse things to come. I think I know what you are describing and I would probably take a close look at the ejector. If you still have that piece of brass / case etc w/e see if there was any kind of deformation - and that it was clearly struck out by the ejector.

I'm thinking maybe it pulled the rim off, or the extractor is weak, let go before the ejector bumped it out - it dropped back onto the magazine the forward running bolt slammed it half into the mag, and then rebounded onto the bolt catch.

That would be my guess. So check for a weak/worn extractor, or case deformation.


The magazine would have most likely caused a FEED issue, not an ejection issue. (Like if what you described what you did but it was not a spent round - but a new one in the same position. I would +100 Gold Cups synopsis.)

It's a brand new rifle, when I said 60 rounds, I meant total. I bought it on a whim, as yet a third AR for myself. The magazine is a PMAG that I have probably used 4 times, and after close inspection, I don't think the magazine is the problem.

The case was not damaged in any noticeable way, which it sounds like could argue for a problem with the extractor, or perhaps more likely, for the "odd bounce" theory. I hadn't really closely inspected the extractor or the ejector, so it sounds like a close look is in order.

The rifle generally seems to make a pile of brass not far from my feet - perhaps a little closer to my feet than the other two similar rifles (dramatically different from the SIG556, which piles 20' forward at 2 o'clock).

I assume that when you say "weak" with regards to the extractor, you are referring to possible issues with the extractor spring and the way it applies pressure against the extractor?

[Asmodeus6]

Originally Posted by fwestrom

It's a brand new rifle, when I said 60 rounds, I meant total. I bought it on a whim, as yet a third AR for myself. The magazine is a PMAG that I have probably used 4 times, and after close inspection, I don't think the magazine is the problem.

The case was not damaged in any noticeable way, which it sounds like could argue for a problem with the extractor, or perhaps more likely, for the "odd bounce" theory. I hadn't really closely inspected the extractor or the ejector, so it sounds like a close look is in order.

The rifle generally seems to make a pile of brass not far from my feet - perhaps a little closer to my feet than the other two similar rifles (dramatically different from the SIG556, which piles 20' forward at 2 o'clock).

I assume that when you say "weak" with regards to the extractor, you are referring to possible issues with the extractor spring and the way it applies pressure against the extractor?

Yes. Check the insert and spring. Exactly what I meant. Strip the bolt and see what insert is in there. These are cheap parts to replace even if on a whim to be sure. So it's no big deal regardless.

Now that you said Pmag I doubt even less its the mag. But if you want to be sure flip the cap over and check it. It comes with a feed lip gauge right on it.

What length gas system? Car / Mid / Rifle?
Guessing over gassed Car length gas system with a weak / wrong extractor insert / or spring.

FWIW I have a slick side DPMS upper (16" car) and it does not have a deflector. It whips brass 20' to my 4-5 o' clock.

[fwestrom]

Originally Posted by Asmodeus6

Yes. Check the insert and spring. Exactly what I meant. Strip the bolt and see what insert is in there. These are cheap parts to replace even if on a whim to be sure. So it's no big deal regardless.

Now that you said Pmag I doubt even less its the mag. But if you want to be sure flip the cap over and check it. It comes with a feed lip gauge right on it.

What length gas system? Car / Mid / Rifle?
Guessing over gassed Car length gas system with a weak / wrong extractor insert / or spring.

FWIW I have a slick side DPMS upper (16" car) and it does not have a deflector. It whips brass 20' to my 4-5 o' clock.

Just finished looking it over, and everything seems to be in the right condition. Spring pressures feel fine, so I guess I'm going to settle that it was an odd-ball one-off kind of thing. I think I'll shoot it today and see if I can reproduce it.

Here are a few images so you can see for s---s and giggles.

[Mr White]

The rifle is ruined. Send it to me and I will recycle it into some sort of helpful medical device that will save poor, sick orphans.

[Asmodeus6]

Image(s) Phail.

?

[fwestrom]

Originally Posted by Mr White

The rifle is ruined. Send it to me and I will recycle it into some sort of helpful medical device that will save poor, sick orphans.

ROFL

Sounds like a great idea... I actually design software for medical devices, and can't for the life of me figure out how that would work!

Nice try though!