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