Weird AR bolt lockup issue

themikea

themikea

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This happened the other day at the range and wanted to see if anyone here has had a similar experience or could try and make sense of what happened.

I had an LAR-15 mag with 10 rounds and an open bolt. Dropped the bolt with the bolt release and it seemed to strip and chamber the round. Pulled the trigger, and just a click. I dropped the mag and went to pull the charging handle and couldn't, it was really stuck hard. I looked and the bolt appeared to be slightly back of where it should be. I was able to use the forward assist to push the bolt completely forward, but still couldn't pull the bolt back with the charging handle.

Since I was able to push the bolt all the way forward, I was able to separate the upper and lower. This unfortunately didn't help me get the bolt loose. My main focus was to get the round out of the chamber so I could look the gun over. I re-cocked the hammer manually, re-attached the upper/lower and fired it once I was sure the bolt was all the way forward. It fired with no problem this time.

I fully inspected the bolt, the bolt carrier and gas key, the gas tube, and the chamber area for damage or obstructions. The bolt carrier also passed the 45 degree drop test with the BCG sliding down the upper on a 45 degree angle and locking into position.

At this point I was really stumped. I completely understand why it wouldn't fire if the bolt wasn't all the way forward, but don't understand a situation that would cause the bolt to get jammed like that. Anyone else?

I think it was the LAR mag that caused the bolt not to go all the way forward, since sometimes stripping rounds can be a chore with those mags. Especially since I ran 100 rounds through PMAGs today with zero issues.
 
My guess, somewhat (as in avery little :) )educated as I run LAR mags as well, and only have problems with them on the top round (10th - I count backwards: bottom round, last, is #1) :

The pressure on a LAR mag on a full capacity magazine is pretty high. I think that sometimes the magazine pressure, as the BCG "strips" out the top (10th) round, is strong enough to push the round into strange angles: I often see marks on those top rounds, ones I just remove from the chamber to inspect, that looks like the bullet is 'smashing' up on the locking groves of the barrel extension (am I saying that right?). The marks seem to indicate a lot of 2 O'Clock hits into the groves/slots.

Maybe something like this happened to you and buldged the case enough to lodge it into the chamber? Then once it was fired the case could form to the chamber and be extracted? I have never had a jammed case due to this, but I also normally only fill to 9 rounds max to prevent bullet damage.

My best guess. cou:
 
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Interesting. Never thought of the case being damaged causing the bolt to jam. I didn't think to check the brass after it fired.
 
Download the mag to 9 rds or take it apart and shave from the bottom of the mag follower so you can load 10.5 rds

Pretty common with magazines.
 
Was it norinco ammo you were using? I found the norinco brass to be a little on the soft side and a little easy to deform. I had this problem on my VZ 556 when I was trying to get the feeding right , it would deform some cases on feeding that would then get jammed in the chamber.
 
Another possibility I've encountered that had the same symptoms you've described was out of spec ammo. Specifically the diameter of the neck of the bullet was 1 thou over saami spec. This caused the a hard lockup like you described that could sometimes be helped by the forward assist. Depended on exactly how much the case neck was oversized. I fixed the probem by turning down the oversized necks.
 
You are describing a hard extraction issue. The round was chambered and would not extract. To me, you made the immediate situation worse by forcing the round in the chamber with the forward assist.

1) The round that was chambered was not properly sized and/or damaged. What type of ammo was used? I've had the same problem with handloads that were not full length sized properly.
2) Instead of jamming the round in the chamber fully (what if it had a dead primer, or you could not get it 100% chambered) you need to extract the round when in binds up. Either gently use a mallet on the charging handle to move the BCG back and extract the case or mortar the rifle on soft ground. In this case you fully collapse you stock (if so equipped) and bang the butt on the ground or some other similar firm surface while pulling down on the charging handle. Either method can provide enough extra force to pull the case loose from the chamber.

Forcing a stuck case further into the chamber is usually a very bad idea. The forward assist is a double edged sword and I don't use it cause it has caused me more problems than it has ever solved.
 
Bolivar said:
You are describing a hard extraction issue. The round was chambered and would not extract. To me, you made the immediate situation worse by forcing the round in the chamber with the forward assist.
Click to expand...

Thanks for the info Bolivar.

It was Norinco .223 that I was using. I have run a few hundred rounds of it through the rifle already with no issues, but maybe just got a bad round.

I agree, in retrospect it was probably a bad idea both to force the round further into the chamber and then fire it. And if it had a bad primer I would have been in a worse situation. My immediate concern was that I didn't have many tools with me and didn't want to move the rifle from pointing downrange with a round in the chamber.
 
Bolivar said:
You are describing a hard extraction issue. The round was chambered and would not extract. To me, you made the immediate situation worse by forcing the round in the chamber with the forward assist.

1) The round that was chambered was not properly sized and/or damaged. What type of ammo was used? I've had the same problem with handloads that were not full length sized properly.
2) Instead of jamming the round in the chamber fully (what if it had a dead primer, or you could not get it 100% chambered) you need to extract the round when in binds up. Either gently use a mallet on the charging handle to move the BCG back and extract the case or mortar the rifle on soft ground. In this case you fully collapse you stock (if so equipped) and bang the butt on the ground or some other similar firm surface while pulling down on the charging handle. Either method can provide enough extra force to pull the case loose from the chamber.

Forcing a stuck case further into the chamber is usually a very bad idea. The forward assist is a double edged sword and I don't use it cause it has caused me more problems than it has ever solved.
Click to expand...

Sounds like this is most likely the case, since the OP said he dropped the mag and was trying to extract the round from the chamber, vise load a round... I heard sometimes the Norinco ammo can cause some problems... maybe get the chamber checked by a gunsmith to make sure you didn't damage it?

Oh hate to ask, but was your AR lubed up and everything? Or were you running it dry?
 
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