Need help diagnosing a problem with my rifle...
I took my new upper out for the first time today. Shot 60 rounds 5 rounds at a time just to get a feel for it and everything was fine. I loaded 20 rounds in a 30 round mag and that's when the problem started. It would fire one round and the bolt would get stuck open about 1/4" and it wouldn't extract. I had a hard time pulling the charging handle back to get it to extract. I fired 40 rounds like this and quit. I took the bolt apart and didn't see anything wrong with it or the extractor.
The rifle is a 14.5" LMT M4 upper with LaRue 9.0 and gasblock. I'm running a LMT standard M16 BCG with Crane O ring and a PRI Gas Buster charging handle. The lower is an LMT with 2 stage trigger and stock carbine spring/buffer. The mags were 2 D&H black teflon with gray Magpul followers and 1 Labelle gray teflon with brown Magpul follower.
Any ideas? Thanks!