I have an AR15 that was built up:
Bushmaster 24" NM H-Bar, 4150 chrome-moly steel with stock A2 front sight/gas block (no-ban)
RRA A4 upper receiver
RRA lower parts kit
Ameetec Arms lower
Wolff Action Spring
Wolff Extractor Spring
MacFarland 1-piece gas ring

Using Wolf 55gr JHP (green lacquer coated case, no neck sealant) will result in 99% FTF after the first shot.
Using Winchester 45gr JHP varmint rounds will result in a 50/50 FTF. I had one actually get jammed so badly the bullet was coming out of the case.

Using XM193 (Ammoman) or M855 (Sportsman's Guide) results in proper function. However, the M855 was working great 99% of the time. There were about 2-4 FTFs where the bolt did not go back far enough to feed another round.

The Mags are SA80 / T-65 steel mags with Magpul followers. They had some problems working with the 45gr varmint rounds but possibly because the cartridges are "shorter" than the M855. The M855 cartridges were barely touching the edge of my mags while the varminter rounds were smaller and could move around.

Forest was patient and addressed a few of the problems:

1). Possible gas hole isn't drilled correctly or aligned with the gas block hole correctly.
2). MacFarland gas ring is causing problems
3). Gas key screws are loose or broke off

Some additional information:
I've used Wolf w/ the stock 3-piece gas rings and ran into the same problem.

The gas key screws are staked by RRA and I checked the torque so they're not loose. The gas key is tight.

The bolt moves around in the bolt carrier like it normally should even with the MacFarland gas ring installed.

Any ideas?

Originally Posted By Tweak: describe the failure to feed? bolt over base? stubbed round? three point bind?

The round will be halfway loaded into the chamber and looks like it overshot the feed ramp, and the bolt slams into the case. It will form a long "streak" and stop by making a huge "gouge" into the case.

Another FTF is when you fire the first round (Wolf for example) and the bolt doesn't come back far enough to load the next cartridge or latch the BHO when it's the last round.

It got to the point where I had to shoot Wolf in single loads only (1 Wolf rd per mag) otherwise I'd run into frequent jams.

Originally Posted By Tweak: does the bolt lock back when you fire the last round out of the magazine?

99% of the time with the M855 (5.56N)
100% of the time with XM193 (5.56N)
0% of the time with Wolf 55 gr JHP (223 Remington)
50% of the time with Winchester 45 gr JHP varmint (223 Remington)

I looked at the FAQ but couldn't find solutions to short stroking.
Forest said it's probably the gas hole not being drilled properly.
What size should it be drilled? It's a 24" barrel with a rifle length gas tube.

Since my gas key bolts are staked, what happens if I remove them and re-torque them? Do I need to re-stake?

I read through minuteman's ordeal and it looks like it might be the Wolff XP action spring causing the problem. I also have a Wolff XP extractor spring and the Crane O-ring.

From his problem, it appeared over-action might be the culprit since when he used a heavy buffer to slow the action, it functioned properly.

On my rifle, I noticed that when the rifle is fairly clean, the Wolf ammo may either cycle properly or the carrier will catch the BHO catch instead of the bolt lugs. All cases are extracted properly although when in heated rapid fire, the cases will come out at the 1-5 o clock positions inconsistently. After 400 rounds, the rifle would not cycle properly after firing each Wolf cartridge. I was basically using a bolt-action rifle having to manually feed the second round OR trying to fix a jam.

I'd like to think Bushmaster set up the barrel, gas port, and FSB properly. I am using their gas tube with their gas tube pin. The "mushroom" is worn out all around on the gas tube.

Originally Posted By metroplex: The "mushroom" is worn out all around on the gas tube.

you need to replace the gas tube then, you're losing a lot of gas right there. solve the short stroke first as it will exacerbate any other malfs.

don't shoot your rifle.

you can make it last longer by insuring that the gas tube is properly alined with the carrier key

gas port is the same size on 20" and 24". you need to mic the end of the gas tube and compare it to the ID of the key. if the FSB is pinned on pulling it off and reinstalling it won't change the alignment. on the BFI barrels you can pull the FSB and look at the spot of Parkerizing left on the barrel by the internal gas port in the FSB, the spot should be centered on the gas port in the barrel. While you have the FSB off check that the holes in it line up with the holes in the gas tube.

where are you located, I can get ANY ar to run, I am in monroe, come on down and we will get her going

Tim

what is the OD of the tube?

ttt for the night crew zzzzzzzzzzzzzzzz

Hi Tweak

I removed the gas key screws before, checked the alignment, and applied High Strength red threadlocker (the stuff I use on my ring gear bolts) and torqued the screws to 40 in-lb. I noticed that RRA did not properly stake one of the bolts but the key did not "feel" loose in the beginning.

This is my only carrier and I haven't pulled the FSB.