AR-15 is having cycling problems

Pietro Beretta

Pietro Beretta

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The rifle is a Bushmaster XM15-E2S (AR-15 A3 Shorty Carbine). I've had it for 3 years and have discharged over 3,000 rounds though it with ZERO problems.

Just last week I took it to the range and to my shock I had a big problem. It would fire the chambered round, and would eject it, but it didn't have enough energy to push the bolt back far enough to peel a fresh round of the mag.

The problem has nothing to do with the magazines...I then thought it could be the ammo, but very unlikely (Winchester USA 62. FMJ). I'm almost 100% certain it has to do with the gas system. Just before I took Bushy to the range, I gave him a detailed cleaning. There was a fair amount of "GSR"/powder/fouling on the actual bolt itself (Excluding the carrier) So I used some solvent and a brush and brushed the rear of the bolt opposite the bolt face...the part just behind the gas rings. THIS is what I believe I messed up.

I think I moved/tampered the positioning of the gas rings (If thats even possible) so when the rifle is fired, the required amount of gas needed to unlock the action is being restricted so when it finally does open, the enegy needed to push the bolt back and operate the action has been depleted...thus f*ck'n everything up.

What role do the gas rings have???
How do they operate???
Do they have to be aligned in a certain position???

I've noticed each gas ring has a little slot...do they have to be seperated in equal spaces, or can they be however/doesn't matter???

I dont know whats up...but I'm pissed, I hope I can fix this with relative ease.

Any help would be appreciated
Thanks,

Pietro.
 
Check and make sure your gas tube is straight and centered.

Mine had been bent and was showing the same symptom.
 
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Gas rings gaps should be staggered as much as possible. They serve the same function as piston rings on an engine - they prevent gas 'blow-by' and create a seal so gas doesn't leak past them.

However, I doubt that one gas ring out of alignment would cause fail-to-feed issues described.
 
+1 what canucklehead mentioned, check to see if your gas rings are properly staggered. the gaps should not be lined up, otherwise the gas will escape.

let us know if this helps
 
I think its both

I think you might all be right about the gas ring issue. Like it was said, make sure you rings are all staggerd. One not staggard won't cause a problem, but all three aligned will. You can do this by hand. Just move them seperatly.
But for sure I think your biggest problem is the gas system. When was the last time you sent a Pipe Cleaner into your gas tube? Do this in all areas that you can. The key on the bolt, where it enteres into the gas tube, and the gas tube itself. Send the pipe cleaner as far into the tube as you possibly can. If its built up; like 3000 rnds will do if not cleaned regularly; not enough gas will get through causing you to have problems with your bolt and not chambering your next round properly.
Finally my last suggestion is to make sure you do a REALLY GOOD post fire cleaning on your rifle. Remember that especially in summer, your rifle will bleed residue back out making it look like it hasn't been cleaned in a while. So when you do a post fire, clean later on in a week or two and you will find that it is really dirty again from all the bleeding.
This all should help you out and fix your problem.
 
Sounds interesting.......MIKE K & PaveHammer, I'm sorry but your wrong. After I experienced this problem, I replaced the Endine recoil buffer with my stock buffer and there was no difference what so ever.

And as for cleaning the key on the bolt, and the gas tube...I clean them regularly...and I dont think the gas tube it bent. I'm stumpted.
 
The problem is certainly a lack of gas, as the rifle is shortstroking.

You might wanna try soaking your gastube overnight in a cleanser, then blowing it out with a can of compressed air. Clean the bolt and carrier much more thoroughly than you usually do.

Something a bit more dramatic would be to pound out the FSB taper pins, rotate the FSB 180 degrees, and use a toothpick to push anything out of the gas port that may have built up. This is a common problem when shooting sub-caliber kits, as the lead fouling can really start to clog things.

Just something else to try.
 
Easy one to diagnose.

The rifle was working fine (3000 rounds) only recently is it now causing you a problem.

I'd bet money the problem is the rings.

Most definitely a problem since you said you just gave it a really good cleaning; there'd have been a previous buildup of carbon which would have helped the seal but that carbon is gone and the clearance is too great.

Same analogy of the automobile piston ring earlier. The wear gets too great and the gas blows by (not enough pressure to cycle properly).

Replace the rings and it'll fix the problem - I'd bet $5 on it :)
 
Sounds like gas.

1. Check the gas key screws, make sure that they're tight.
2. Check gas rings...simple test...slide the bolt back and forth, if there's little or no ressistance replace all 3
3. last to check if not the barrel is not Chromium or Chrome lined....check the chamber for pitting...will give off the same results of lost gas.

Cheers
Bill
 
IDPACONVERT said:
Sounds like gas.

1. Check the gas key screws, make sure that they're tight.
2. Check gas rings...simple test...slide the bolt back and forth, if there's little or no ressistance replace all 3
3. last to check if not the barrel is not Chromium or Chrome lined....check the chamber for pitting...will give off the same results of lost gas.

Cheers
Bill
Click to expand...

That sounds more on target...when I slide the bolt back and forth, there is little resistance. How do I replace them??? Do I just pry them out and snap the new ones in, or is there a special way???
 
I have just ordered a McFarland 1 Piece Gas Ring which is suppose to be the BEST!!!.... this is there statement:

Stops Gas Leaks & Eliminates Sluggish Bolt Performance
Single spiral of spring steel loops around the bolt three times and leaves no path for gas leakage. Replaces conventional three-piece “piston ring”-style sets that can accidentally line up, causing a major leak from the gas expansion chamber in the carrier.

Hope it works I'll let you guys know.

Thanks for your help guys,
Pietro.
 
Gas rings are a "wear" item on an AR-15 and as such every owner of an A-15 should have at least one spare set. They are dirt cheap, so don't be stingy.

Also when cleaning the gas chamber and the mating part of the bolt, its important to not damage the rings or align all the gaps (as has been mentioned).

When working on the bolt the rings to tend to naturally migrate to having the gaps aligned.
 
If you can hold the assembly up by the bolt,, and the carrier doesn't slide back,, then your rings should be good enough.

Borrow someone elses bolt and shoot it. If it works,, you have isolated the problem to the bolt (gas key or rings).
 
Problem Fixed!!!....but what a pain, and $60.00 plus gas and time...but very worth it. After ordering the new gas ring system in, I went to the range and the same problem was happening...so I took it to my local smith, and he took the whole bloody thing apart..gas tube and all...and cleaned each part and hole on the upper reciever.

I took it back to the range, and the same bloody problem, so I then isolated the problem to the bolt/carrier assembly. And thats when we found out the problem. The two srews on the carrier key were loose, and weren't staked in proporly at the factory (I was told) so they were tightened and re-staked.
It wasn't cycling properly because gas was leaking/escaping from the loose screws on the gas key on the carrier. After they were tightened...PROBLEM'O FIXED.

I went to the range and dumped out 300 rounds of WinUSA 62.gr FMJ threw my puppy flawlessly!!!....lets just say, I'm a happy camper.
 
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