Unlocked bolt, frozen carrier.

Gun: Geissele URGI 11.5
Muzzle Device: Surefire RC2
Buffer Spring: Super 42/H3 buffer
Ammunition: Winchester M193/PMC Bronze 223

Shooting up until I get a click and no bang. Look at the chamber, bolt is unlocked but stuck. Can't mortar it out, ended up hammering it out with a punch. This isn't the first time something like this has happened. When I first got the upper it wouldn't chamber and I'd have to mortar it out. It would shoot fine for a few rounds then just lock up completely. The ammo I'm using works just fine in three other uppers. Does anyone have any insight as to what is happening? I think it's an ammo issue because the ammunition the upper is zeroed for works just fine.
Gonna add a little update.

Swapped the Super 42/H3 for a Sprinco Blue/H3 and that seemed to help for the 30 rounds I shot.


Did you check the head space? Is it a super duty upper with the enhanced bolt? If I was having issues with extraction and having to mortar rounds out I would stop shooting that ammo, clean everything, and look for what was causing the stoppage. My 11.5 super duty upper with the super 42/H3 buffer shoots 5.56 unsuppressed all day. What are you using for lube?
Digging through it with the dudes on Arfcom while I wait till tomorrow for GACS to respond. Seem to think it's a headspace issue. Rounds won't fully seat and require a cleaning rod to pop them out. It'a URGI 11.5 with the REBCG. The ammo works just fine in every other gun I've shot it through, including my 14.5 URGI. Sounds like I've just got a lemon.