AR Cycling Problems

[Garrett]

I just got back from the range. I was shooting my 16" AR off sandbags checking out a couple of loads. I shot a bunch of groups and everything ran fine.

I wanted to shoot some off-hand groups before finishing. As soon as I started shooting off-hand, the gun would start having failure-to-feed malfunctions. The bolt would ride over the top round in the mag. The front of the cartridge would be started into the chamber, but the back end would be smashed under the bottom of the bolt.

I found this odd that it would start doing this when I started shooting off-hand, but had cycled flawlessly from the bench. I was using the same ammo and the same magazine. I switched mags but the problem persisted. I sat down and tried shooting from the bench again, but it was still having problems.

Could it be possible that I got some crud clogging the gas tube so the bolt carrier is not cycling fully? Is it possible that this just happened as I finished shooting from the bench and went off-hand?

The gun had maybe a total of 150 rounds through it since last being cleaned.

Any ideas?

[Chriss Grube]

Could be crud the gas rings might not be lined up properly which will cause the same type problem. Give it a good cleaning including the gas tube and see if it cures it. Some powders will deposit more crap than others.

[a-44978]

Even if you don't find the answer your asking in the right place.

I've been down this road on ar15.com and got brow beat right outa there!

The round looks like a banana when you get it out right?

My ARMALIE was doing this and some other stuff

They blamed ammo ,I guess lake city was'nt good enough because that is what i like to shoot

The short cycling issue was eventually repaired by bushmaster who repaired a gas leak at the front gas block(post)

Come to find out this rifle had a tight .223 chamber and did not like Q3131 ammo.(this not being the cause of the cycling prob)

More details can be had via pm,i get mad just thinking about it

Bushmasters rock and the companys service department was great to me fixing a rifle they did'nt build in the first place!

[TBF]

Sounds like a short stroke problem to me also.

Check to see that the bolt locks back with every shot, if not you have a short stroke.

The usual suspects, in no particular order:

Crud , dirty chamber, dirty carrier , etc.

Gas problems, plugged gas tube, or leaks at front sight base or carrier key, look for soot marks. also check

top of gas tube with a small piece of broken mirror for excessive wear. Check gas rings etc.

About how many rounds have YOU shot through this rifle?

I ask because it would help to know if this particular rifle started something new, or if it could be an old problem...

Good luck,

Travis F.

[benny hill]

you are limp shouldering the gun & causeing it to short stroke while standing but not the bags were you were leaning into it. try leaning into the gun & pull it into your shoulder.

[Garrett]

you are limp shouldering the gun & causeing it to short stroke while standing but not the bags were you were leaning into it. try leaning into the gun & pull it into your shoulder.

I don't think that was the case. I had not been pulling the gun into my shoulder on the bench, but was letting it "free recoil". When set up on the bags correctly, this can translate to better accuracy as you are having less influence on the differences in how the gun recoils. (supposedly)

After the first malfunction, I pulled the gun tighter into my shoulder. Then I changed mags. Then I tried shooting from the bench again. All still produced the bolt-over jam.

I just tore the gun apart. The key is still on tight. The gas rings were not all lined up. I didn't have crud built up in the key or on the end of the gas port. I really don't want to pull the gas block off.

I'll clean the gun, and hopefully get a chance to dump a couple of rounds through it this weekend.

[TBF]

Usually no need to pull gas block, unless you really feel the need. Blow compressed air through the gas tube, I suppose it would be advantageous to have done this on one that was working to know what it usually is like, but in serious cases blockage is obvious.

AR's ain't rockets, but on occasion they can make you cuss.

The common problems fall into four categories (for short stroke problems )

1. Ammo ( I suppose you already have eliminated the obvious? )

2. Mag ( Probably not your problem, You swapped mags. )

3. Mechanical. Something won't move easily enough, dirty or damaged.

4. Gas. Either a leak ( loose, worn or broken parts ) or something is plugging up ( dirty ).

Good luck.

Travis F.

edited to add ( for short stroke problems) as without that , it makes no sense...

[kurtm]

Garrett:

Couple of quick checks. I don't know how many rounds you have through it, but it shouldn't matter. Check the "ball" end on the gas tube where it comes through into the reciever area. I had one that got a big nick in it and it quit running. Lube the heck out of the main spring and tube and check for cracks on the pin holes on the upper ( this would be real rare!) Replace the gas rings! for the $2 bucks this costs it,s cheap insurance!! The load you are testing could be right on the edge and once it gets hot it is not creating enough pressure ( this is really clutching at straws) I look at gas rings like plugs in a race bike, the minute it gets hard to start or loads up in the mid range ...throw them away...same for ARs the minute it short cycles ...throw them away!!! Last but not least check your buffer ( easy to do since you have it pulled apart to lube the heck out of it) Make sure it clunks when shaken and the polyurethane piece is still intact. Good luck and let us know! KURT

[Garrett]

I tore the gun apart last night and cleaned it. The gas tube looked fine where it pokes through into the receiver. The key also looks fine. It is on tight and secure. Neither have an accumulation of crud.

One possible culprit may have been the buffer tube. I removed the stock and the buffer tube was slightly loose. It wasn't unscrewing, it just was not tight. This may have been loose when I was shooting. Of course, it may have just loosened when I unscrewed the stock retainer screw at the back end of the buffer tube. Don't know. I wiped down the threads of the buffer tube and put a couple of dabs of blue locktight before reinstalling.

I lubed the poop out of the buffer and spring. The buffer was still in great shape. No noticable deformity on the back end. It would still clunk back and forth.

One of the mags I was shooting with did have a weak spring. It won't reliably hold the bolt open after the last round. This was a 20 round Colt mag. The other mag I had used was a 30 round contract mag. It still seems to have a good spring.

I shot the gun today with the same two mags. I shot what was left of the ammo that I was shooting the other day when I started having problems. I also shot some S&B and some Winchester white box. Maybe 100 rounds in total. I tried holding the gun as loosely as possible, to try and induce a "limp shoulder" malfunction. The gun ran just fine no matter what I did. I tried holding the bolt lock down as I fired to be sure the bolt was going all the way to the rear. It would lock back every time.

So the gun seems to be happy (at least for now). I'm still a little confused about why it just stopped running all of the sudden. But it seems to have gotten over it.

Thanks everyone for all of the help.