short stroking

[kgj1119]

While at the range the other day, I had fired a couple hundred rounds. I made sure the bolt carrier was lubed, and everything was in working order every 100 rnds or so. At the end of the day, the it started short stroking. At first I thought it was the mags, but that wasnt it. I cant figure out what it might be. It fired all day without a problem. I used the same Black Hills ammo all day long. Could it be that the chamber had too much lube, and the heat had something to do with it? Can somebody give me insight to what could be wrong?

[Moose]

Short stroking is caused by one thing; something robbing the energy from the carrier group preventing it from working correctly - you need to find out what is causing the energy loss.

Unfortunately you don't give enough information in your post to help that much; were the rounds ejecting normally but the bolt wasn't picking up a new round? The more information you can give, the easier it is to diagnose the cause.

ETA Check the Short Stroking Sticky above

[kgj1119]

The bolt carrier wasnt travelling back far enough to pick up the next round. It only went back about half way.

[Robb Jensen]

The bolt carrier wasnt travelling back far enough to pick up the next round. It only went back about half way.

More than likely it's leaking gas somewhere. The most common place is at the carrier gas key. 2nd most common if you don't have a pinned FSB is a loose gas block. And 3rd is a bad gas tube. The first signs of gas leakage is failure of the bolt to lock back when the rifle/carbine runs empty.

[Stephen_H]

More than likely it's leaking gas somewhere. The most common place is at the carrier gas key. 2nd most common if you don't have a pinned FSB is a loose gas block. And 3rd is a bad gas tube. The first signs of gas leakage is failure of the bolt to lock back when the rifle/carbine runs empty.

Agreed. Check the carrier key and the gas block.

Stephen

[conspiro agnew]

The only time I've ever experienced this was when the gas key came loose on an old bushmaster BCG I had. The key was not staked, before I knew what staking was, and eventually came loose. Before I figured out the problem, I had already ordered a replacement LMT BCG and later a friend came by and showed me the problem with my BM one, and fixed it.

One good reason though to have an extra BCG.

[AR15barrels]

And 3rd is a bad gas tube.

I have a picture of what that looks like...



Notice that the gas tube's "mushroom" is completely worn off on one side of the tube.
This is caused by poor barrel nut alignment or a gas tube that was bent during installation.