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  #1  
Old 03-22-2009, 06:42 PM
Ytka Ytka is offline
 
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Default AR 15 won't chamber a new round

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.
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Old 03-22-2009, 06:56 PM
Outsydlooknin75 Outsydlooknin75 is offline
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Sounds to me like its short stroking. Check for a loose carrier key. If loose tighten abd restake.
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Old 03-24-2009, 07:52 AM
rockdawg rockdawg is offline
 
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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.
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Old 03-24-2009, 08:46 AM
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I have the same problem with my bushmaster.But i dont know what to check.
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Old 03-24-2009, 09:23 AM
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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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  #6  
Old 03-24-2009, 10:54 AM
Outsydlooknin75 Outsydlooknin75 is offline
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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.
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Old 03-24-2009, 12:51 PM
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I had an issue with a 6.8spc ar upper and it turned out to be gas rings.
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Old 03-24-2009, 02:13 PM
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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.
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Old 03-24-2009, 02:24 PM
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DYI, Did you stake that bolt? That thing is sure enough staked!!!
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Old 03-24-2009, 04:02 PM
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Quote:
Originally Posted by georgiaboy View Post
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:

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  #11  
Old 03-24-2009, 07:56 PM
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Quote:
Originally Posted by georgiaboy View Post
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.
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Old 03-24-2009, 08:45 PM
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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.
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Old 03-24-2009, 08:57 PM
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Quote:
Originally Posted by georgiaboy View Post
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.
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Old 03-24-2009, 08:59 PM
Craig Knight Craig Knight is offline
 
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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.
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Old 03-24-2009, 09:15 PM
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Thats my problem, WOLF!
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  #16  
Old 03-25-2009, 01:11 AM
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Quote:
Originally Posted by Ytka View Post
...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.
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Old 03-25-2009, 02:26 PM
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Quote:
Originally Posted by Steve762us View Post
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.

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.
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Old 03-28-2009, 08:49 PM
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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.
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  #19  
Old 03-28-2009, 08:56 PM
Outsydlooknin75 Outsydlooknin75 is offline
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Quote:
Originally Posted by georgiaboy View Post
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?
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  #20  
Old 03-28-2009, 09:06 PM
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Quote:
Originally Posted by Outsydlooknin75 View Post
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.
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Old 03-28-2009, 09:11 PM
Outsydlooknin75 Outsydlooknin75 is offline
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LOL .... you mena that Brian and Sean have more than one friend LOL. I talked to Sean the other week about borrowing it and he said a friend had it ....... I figured it was you.

I cant do the rifle steel challenge tomorrow. I will actually be in Dawsonville for a birthday party at 2. So that blows that idea.

I cant hit nothing with irons anyhow. I would be throwing lead downrange for nothing.

Although I did pick up 500 M855 bullets the other day that I need to load up ...... I would just blame it on you that you shot the holes in it.
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  #22  
Old 03-28-2009, 09:32 PM
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I like shooting irons, I will try to make the next one. Creekside is a long ride and I try to go to church with the wife and baby so Sundays are tough.

I actually have a buddy's swager (not Sean, ha ha) but it doesn't work well. I seriously don't decrimp much at all. I hate crimps, I have broken too many .308 pins on them and RCBS is tired of sending me free ones!
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Old 04-20-2009, 09:24 PM
Ytka Ytka is offline
 
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I have finally narrowed the problem down to either the gas tube or the gas block. I checked the gas keys and they are tight. I also made sure the gas rings weren't all lined up. I borrowed a friend's AR and switched pieces until I figured out what made it stop working. As long as my upper was involved, it wouldn't function. The bolt didn't seem to affect it at all.
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Old 04-20-2009, 09:28 PM
Outsydlooknin75 Outsydlooknin75 is offline
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The gas block/front sight base might not be lined up correctly with the gas port in the barrel...... or the gas port itself could be undersized as well.
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Old 04-20-2009, 09:37 PM
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You can check alignment of the gas tube and bolt carrier using a small drill bit that will fit inside the tube.
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