View Full Version : AR-15 short cycling problem

January 2, 2010, 06:40 PM
Today I took a newly assembled AR upper to the range and had some short cycling problems.

It's using a Daniel Defense 16" barrel that I got with an FSB installed from Bravo Company.

The gun was assembled with a JP Enterprises muzzle brake, for no other reason than I'd had it laying around for a couple of years, and the lower I put it on has an A1 stock with an Enidine buffer in it. No real plan to build a kickless AR existed, but that was the combo I took to the range. Initially it ejected spent casings, but did not feed the next round at all. Fortunately I had another gun with a standard buffer and with that it cycled 18/20 rounds.

The barrel install went well and there are no apparent alignment problems and no apparent binding of the bolt carrier or gas tube.

I'll try another bolt carrier on the chance that there is some leakage.

One thing I'm wondering, though - since with a standard buffer it seems to be right on the feather edge of cycling properly, could a muzzle brake affect the gas charge to the system and inhibit the cycling?

Other ideas are welcome. I'm hoping I can remedy it short of attacking the gas port, but I'll do that if need be.

Ammo was M855.

January 2, 2010, 06:44 PM
Did you check the bolt carrier gas key?

LongRifles, Inc.
January 2, 2010, 07:14 PM
If you are using legit M855 ball ammunition then that rifle should have no problem with cycling if all the parts are right. It's a higher pressure cartridge vs shelf bough 223 Remington.

As stated, check your gas key and ensure it is tight and STAKED. Make sure the gas tube "bulb" is aligned with the hole of the key. If the tube is worn it can cause short cycling.

Make sure your gas rings are in good shape. It's rare, but these can cause the gun to sputter also.

Do you have the right buffer? Make sure you don't have a mechanical problem that physically prevents the bolt from coming fully to the rear.

A direct gas operating system is a little more sensitive than piston types, but a muzzle brake/compensator should have no influence. All your gas pressure drops to near atmospheric the split second that bullet leaves the crown.

Make sure your gas block/front sight assy is timed to your gas port in your barrel properly. If it's out of clock position it will choke the pulse going to the bolt carrier group.

good luck.


January 2, 2010, 08:05 PM
When you put the A1 stock on, did you also use an A1 stock screw?

If not, the gun will give you what seems to be short stoke malfunctions, sometimes a lot, sometimes not. But it can and will drive you crazy. :)

Bartholomew Roberts
January 2, 2010, 08:20 PM
Could be a combination of new gun + too heavy buffer with the Endine. Was it pretty well lubed?

Other than that, it seems like you are looking in all the right places and have the right plan on what to try next.

January 2, 2010, 09:26 PM
I do have a new bolt carrier in it now, although the other didn't show any signs of leakage. And I do know about A1/A2 stock screws, but thanks for the reply.

The hope is that I won't need to pull the FSB and right now I'm of the mind that it may just sort itself out in about 100 rounds or so, as new guns often seem to do. I am convinced that the Enidine buffer in this combo just isn't going to work.

Kicked like a newborn kitten, though.