When I went shooting last week, my SBR starting short stroking for no discernible reason. Everything was relatively clean, well lubed, and it had never had problems before. Unfortunately, I had no spare parts or tolls with me, so I was kinda screwed on troubleshooting.
I took it home that night and cleaned the crap out of it, and relubed everything. Couldn't find any worn or busted parts, so I figured that maybe it was chamber filth from the steel cased Tula.
This week, I hit the range again - same problem. This time, I had spares. I swapped in a carbine buffer in place of the H2, no joy. Swapped out the BCM bolt carrier group for a crappy, worn out DPMS, and the gun ran.
Dropped the H2 buffer back in, gun still ran.
So, I swapped the BCM bolt into the DPMS carrier, and vice-versa. BCM bolt + DPMS carrier, and it ran. BCM carrier with DPMS bolt, no joy.
When I got home tonight, I started going over the BCM carrier. No obvious burrs or bad spots inside the carrier, so I checked the gas key. The staking on the front screw looked a little weak, so I checked the screw. One tiny bit of pressure later, and the damn screw turned.
To quote one of my favorite TV shows - "Well THERE'S your problem!"
So, I tried to tighten the screw down more...
This damn thing is stripped!
I can't get the screw out because of the staking, but the staking wasn't enough to stop it from spinning.
Lesson learned - Even BCM can screw (heh) up every now and then. I've only had this BCG for about 6 months, and it's only seen about 500 rounds (work has been a ***** lately), so it's definitely not due to use or abuse. I've already got an email in to them, so I guess it's wait and see to find out what they are willing to do to fix it.
Second lesson learned - it doesn't hurt to double-check gas key screws, even on bolt carriers from higher end companies. Just because it LOOKS staked doesn't mean it's really secured.