06-20-2011, 01:03 PM
Shouldn't be the buffer or spring. What do you mean by failure to cycle? What happens after it fires? Does the case eject but the bolt isn't going to the rear enough to chamber a new round or does the bolt just barely unlock? Sounds like a gas issue to me. Make sure everything is in alignment(the gas block, gas rings etc) Who did the build? How many rounds have you put thru it? Take the gas block off, make sure the port in the gas block lines up completely with the port in the gas tube. Doesn't take much misalignment to make it malfunction.