As an anecdote or background, I have shot 10,119 rounds through various combinations of 7 lowers, 10 uppers (spanning 3 calibers), and 8 silencers and today was my first failure that resulted in "stoppage". I have had a few failures to lock the bolt back with old straight 20rd p-mags on my 300blk but that's it. So I have had very good fortune with this platform using good mags and good ammo (and good parts). But this failure is interesting and I can't quite figure it out.
The rifle in question is a 10.3" Colt barrel (w/ C7 type upper) using a Specwar 556k shooting PMC X-Tac 55gr from a 30rd P-Mag.
Illustrated here:
-Loaded a mag on a closed bolt
-Chambered a round via charging handle
-Fired the first round fine, hit where it should
-Went to pull the trigger again and no bang (can't recall if the trigger had reset or not)
-I assumed it was a failure to feed and charged the rifle again, seeing nothing in the chamber, but the bolt didn't go all the way into battery once I released the handle.
-Pulled the mag and tried to charge again but the bolt was stuck
-Mortared the rifle on the table using minimal force and out popped an unfired round that had a dent on the body extending to the shoulder
-Pulled the bolt and handle and inspected the chamber, bore and silencer. Nothing unusual.
-Rifle functioned fine after that
What I think happened was the first round extracted and ejected fine. But the second round never got fed. Nothing in the chamber. I charged the rifle again, it picked up the second round but only fed 90% of the way and got hung up causing the bolt not to go into battery.
Maybe the mag was not fully seated being that it was loaded to 30 and inserted on a closed bolt, and that caused the round to not feed and then mis-feed?
Either way I thought it was an interesting failure and one that caught me off guard. Trying to learn from it and figured I'd share.