Originally Posted by
knfmn
Not to be simplistic, but are you 100% certain that the gas tube/block are aligned right? I know you said you blew through the tube and it seemed ok, but let me share my recent experiences. I built an AR. I'm pretty anal about things, so I was super careful to make sure that everything was just so. I finished it and took it to the range and experienced exactly what you experienced: it wouldn't eject the brass. I tore the whole thing apart repeatedly over the next few weeks, pulling my hair out trying to find the solution. I changed the gas block for a very expensive one out of desperation, which is not an easy proposition in MA, since our muzzle devices have to be pinned and welded, meaning the old muzzle brake had to be ground off, the gas block changed and a new one pinned and welded on. Anyhow, after all that, what I discovered was this: when the handguard was put on it was putting enough force on the gas block to shift it away from the gas port in the barrel. I took the handguard off and threw it in the trash, replaced it with a free float handguard and the AR runs 100% now.