A friend's AR problems

[Ed L.]

I got this email from a friend in California who has

"I have a 10-year-old XM15-E2S that fails to cycle most of the time these days. (It used to work fine.)

I think you would call the problem short-stroking. The bolt stops right
after it makes contact with the new round.

Also, the bolt has stopped locking back after the last round is fired.
My guess is that it doesn't travel back far enough to activate the catch.

Pulling back the charging handle, it "feels" like it binds halfway back,
but I have nothing to compare it to, so I'm not sure.

Because it looked dry, I lubed up the buffer assembly but haven't had a
chance to try it yet. It still feels like it binds, though. I'm
wondering if the alignment between the upper receiver and stock is correct.

One more thing: There seems to be a small spot inside the upper receiver
where something has worn away the aluminum."

My suggestion was:

1. Buy a better bolt. I recommended a Bravo Company Bolt (which are out of stock right now) but since he live in California he was leary of buying a bolt made for full-auto, although I assured him it was not an issue. He says it may be illegal under CA law. I don't know about this. If this is the case I recommended he buy an LMT semiauto bolt carrier group.

2. I asked whether he was having problems with every magazine or just one.

3. As for the problem of short stroking, I recommended he buy an H buffer and spring.

Anyone have any thoughts on this?

thanks

[R Moran]

Be honest Ed, its you, right?

What about checking the carrier key bolts.

Bob

[Ed L.]

Nope, never owned a Bushmaster.

Just Colts, a Noveske, and now a HK416 upper.

My friend checked the carrier key and says that it doesn't seem loose and the staking appears to be where t originally was. I suggested that he get a better bolt & bolt carrier as an upgrade and precaution.

[Iraqgunz]

Ed,

I would have him check the bolt carrier first, then I would check my gas rings (after the weapon has been checked for cleanliness) and I wouldn't rule out that he needs a new gas tube. If he has had it for 10 years and not knowing how many rounds it is a good possibility. If that didn't fix it I would then start looking at the buffer and spring. The thing is that it used to work in it's original configuration which tells me that something has worn out.

Do we know what type of ammo he is using and an approximate round count? It could also be gas port erosion in which case he will need a re-barrel job.

[Ed L.]

Thanks,

He has less than 1000 rounds through the gun. Not sure what type of ammo he is using.

[jtb0311]

Be honest Ed, its you, right?

What about checking the carrier key bolts.

Bob

That's the first thing I thought of.

[ST911]

Sounds like a gas problem.

Run the short stroke test and confirm problem.

Gas tube okay? Premptive replacement is inexpensive, JIC.

Tighten carrier key bolts and stake them.

Generously lube and test fire.

Don't install a new spring or H buffer without the above. If you're losing gas, increasing mass and resistance will exacerbate the problem.

Wear in the receiver (shiny spot) may or may not be anomalous.

[5pins]

Ten years and only 1000 rounds. Hell it isn’t broken in yet.

[Mung]

My BM did the same thing w/ Wolf ammo.
Here's how I fixed it: I bought a Noveske.

[Ed L.]

After asking a few questions via email, I received some clarification.

• Gun functioned fine before.
  
• Problems occurred with Wolf and UMC ammo. He initially used UMC, noticed problems, and then tried Wolf, not realizing that Wolf would be more problematical.
  
• Problems occurred with 4 different magazines.

He further clarified about the malfunctions:

"From what I recall, the bolt was stopping on top of the new round as it was coming out of the mag. In other words, the base of the round was lower than the bullet end, and the bolt was making contact in the middle of the case.

That made me think the bolt carrier was moving back far enough to eject the empty but not far enough to pick up a fresh round (or to lock back on an empty mag)."

Of course, my solution is a better bolt & bolt carrier with a better buffer and spring for good measures to bring it up to a better standard.

I believe he will be sending the bolt & bolt carrier back to Bushmaster for restaking/tightening.