AR 15 won't chamber a new round

Ytka

Senior Member
I just bought a Bushmaster two weeks ago. The gun was basically new. I don't think the guy had ever even shot it. We took it out last weekend and shot about 80 rounds through it with no problem. I did notice that it was flattening one side of the case mouth though. Then yesterday I went back to the range with it and it may as well been a single shot. It would fire the first round, the the second trigger pull would just click. It would eject the casing most of the time, but sometimes wouldn't. It would go back just far enough to cock the hammer, but not enough to cycle a new round. Every now and then it acted like it didn't want to pick up the first round when I pulled the charging handle. It was oiled, but not excessively. I did try to add a little RemOil after it started acting up. I used 3 different mags from different manufacturers and 3 different kinds of ammo (Remington UMC, Federal, and Monarch).

Any ideas as to what could be wrong? A friend of mine was there with his AR, but I didn't think to try switching bolt assemblies and/or the buffer assembly with his.
 
Sounds to me like its short stroking. Check for a loose carrier key. If loose tighten abd restake.
 

rockdawg

Senior Member
Also check the gas rings on the back of the bolt to be sure they are not lined up . Were you holding the rifle firm into your shoulder? If the rifle can move with the recoil, it could possibly short stroke.
 

DYI hunting

Senior Member
Carrier key screws should be tights and staked so they can't loosen. Look at the second picture and you can see how they are staked so they can't turn.

There are 3 small rings on the bolt. See arrow in attached picture on where they are at. They have a small gap in each ring so you can install and remove them, they are laying to the right of the bolt. Make sure you have all three rings and spin the the rings on different sides so the gaps don't all line up.

Also check the gas system. Does it have a front sight post or gas block? If it has a front gas block, make sure it is lined up with the gas hole in the barrel and the screws that lock it to the barrel are tight. If it has a front sight post, make sure it is straight and has both pins in it. If the gas block or sight is a little off, you might not be getting enough gas through the gas tube and short stroking.

It could also have something in the gas tube. I remember seeing one that has a bunch of cotton in the tube from someone trying to clean it with a cotton swab and the cotton coming off.
 

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Here is a quick simple way to check gas rings ..... take the bolt carrier group with the bolt still it in...... flick the bolt all the way in the out position.... now take and stand the whole thing upwards on the bolt face flat on a table. If it collapses you need new rings If it stands proud ... you are fine.
 

georgiaboy

Senior Member
I believe the gas rings being in alignment (or not) is a myth. I was taught the same thing at Ft. Benning, but it isn't true from everything I have seen. Just FYI. Anyone else know any info on that?

Ytka, I would borrow a buddy's bolt to try. You might also examine the buffer and spring. If you have an incorrect buffer it may not cycle as well. I bet the bolt is the issue, but is an easy fix.
 

georgiaboy

Senior Member
DYI, Did you stake that bolt? That thing is sure enough staked!!!
 

DYI hunting

Senior Member
DYI, Did you stake that bolt? That thing is sure enough staked!!!

Nope, but I bet it will not be going anywhere. I guess I should have posted a reguler joe factory staked bolt. Your properly staked bolt should look more like this:

StakingJob2.jpg
 

Slingblade

Gone But Not Forgotten
I believe the gas rings being in alignment (or not) is a myth. I was taught the same thing at Ft. Benning, but it isn't true from everything I have seen. Just FYI. Anyone else know any info on that?

That's the same thing that I was told; Combat Arms said that if you want to stagger them that was fine but was not really needed.
 

gyppo

Senior Member
What brand ammo did you shoot. If it was corrosive you may have problems. There is usually a reason why ARs shoot fine one outing and fail tofire the next.
 

Steve762us

Senior Member
I believe the gas rings being in alignment (or not) is a myth. I was taught the same thing at Ft. Benning, but it isn't true from everything I have seen. Just FYI. Anyone else know any info on that?

Ytka, I would borrow a buddy's bolt to try. You might also examine the buffer and spring. If you have an incorrect buffer it may not cycle as well. I bet the bolt is the issue, but is an easy fix.

Staggering the gas rings seems like "a good thing to do, while you're in there," but probably not that big of a deal. I had the opportunity to fire thousands of rounds of 5.56, courtesy of Uncle Sam, and many times I'd find my ring slots lined up, when cleaning time rolled around---but I experienced malfunction zero, during use.

OTOH, one thing the TMs did spec was to NOT swap bolts, due to the headspacing methodology. I don't know if that was myth or not, maybe some of the "builders" here can comment on that.
 

Craig Knight

Senior Member
my DPMS did that with wolf steel cased ammo, I quit using it, only shot 20 rds thru it to start breaking in the barrel, no rapid firing and then cleaned it real good and it feeds everything else no hiccups or burps. I sold the wolf junk and had no problems since.
 

jonkayak

Senior Member
...3 different kinds of ammo (Remington UMC, Federal, and Monarch).

Some Monarch ammo has a coating on it that will heat up and melt. Then it will re-harden once the gun cools down again.

I had a Bushmaster that would do all sorts of crazy stuff. It turned out to be a wore out trigger. The trigger had wore around the pin that held it in place. The trigger would wobble left to right. Once that was replaced all was fine.
 

georgiaboy

Senior Member
Staggering the gas rings seems like "a good thing to do, while you're in there," but probably not that big of a deal. I had the opportunity to fire thousands of rounds of 5.56, courtesy of Uncle Sam, and many times I'd find my ring slots lined up, when cleaning time rolled around---but I experienced malfunction zero, during use.

OTOH, one thing the TMs did spec was to NOT swap bolts, due to the headspacing methodology. I don't know if that was myth or not, maybe some of the "builders" here can comment on that.

Same here. :bounce:

I have heard the same about bolts although I will admit to swapping bolts on rifles often enough. It is common practice to carry a spare bolt to a match and see guys swapping if a problem happens. I do have a couple of uppers that have had the bolts specifically headspaced to them but I wouldn't sweat changing if I had too.
 

georgiaboy

Senior Member
Update! DYI, I found out how to stake a gas key and make it look like your pic (even and neat). I am sure some will laugh, but I never thought of this method:

I had a gas key get loose at a match awhile back so today I fixed it. I took it off, checked the screws, degreased everything, tightened the screws after Loctite was applied then re-staked.

I staked with a 1/2" hardened chisel. Worked like a charm and it is the neatest staking job I have, including Colt and LMT!

Anyone near me needing a gas key staked, holler and it takes 2 minutes tops.
 
Update! DYI, I found out how to stake a gas key and make it look like your pic (even and neat). I am sure some will laugh, but I never thought of this method:

I had a gas key get loose at a match awhile back so today I fixed it. I took it off, checked the screws, degreased everything, tightened the screws after Loctite was applied then re-staked.

I staked with a 1/2" hardened chisel. Worked like a charm and it is the neatest staking job I have, including Colt and LMT!

Anyone near me needing a gas key staked, holler and it takes 2 minutes tops.

Some of yall arent the quickest on the uptake. Ive been staking em like that for a while now if they needed it.

You done with that Dillon primer swager yet?
 

georgiaboy

Senior Member
Some of yall arent the quickest on the uptake. Ive been staking em like that for a while now if they needed it.

You done with that Dillon primer swager yet?

I am better at breaking than I am fixing!

I don't have the swager (Brian and Sean's I assume) and my crimped brass is in its own container marked DO NOT USE! ha ha. I hate swaging but I may have to start back one day.

If you go to rifle steel match tomorrow, how about some pics and an AAR?!? Sounds like a blast, especially with irons. Oddly enough my irons are zeroed with SS109, not appropriate for the steel match. :rofl:
 
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