I have a BCM which I shot today, and suddenly ran into it short stroking. Filmed a friend shooting my rifle in slo-mo, and the bolt only cycles half of the stroke. Basically, it doesn't even go back enough to eject the empty case, so it goes right back in the chamber.
Fortunately, one of the guys I shot with had a spare rifle, so he let me take use it to run some diagnostics. First, I used my upper on his lower, and the same thing occurred. Thus, I eliminated the buffer and buffer spring as the problem. Then I used his entire BCG in my upper. It then cycled perfectly fine. So now we know it's something within the BCG, and not because of the gas tube being undergassed, obstructed, or out of position somehow.
Did a little more testing, and used his bolt in my bolt carrier. The short stroking occurred again. Then I used my bolt with his bolt carrier, and voila, the gun cycled great once again!
So now I'm pretty sure there is something wrong with my BCM bolt carrier. If I had to guess, it must be something with the gas key. I last used the rifle in June for a 2 day class, and it ran like a champ then. The only thing I have done since then was clean the rifle entirely, and kept it lubed. When I cleaned it last, I ran a pipe cleaner through the gas key, so I don't think it could have been obstructed. But who knows if a piece of the pipe cleaner broke off, or some other crud got lodged in there.
Are there any other suggestions to rectifying the problem? I cleaned my BCG again tonight, and did all I could to make sure the gas key was free flowing, shy of removing the gas key from the carrier. Or should I contact BCM about what they can do about it?
Thanks in advance!
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Originally Posted by Disciple
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