Gas/Jam?

[eldplanko]

Have you tried different ammo and mags?

I'll bust out a box of the good stuff (XM193s) next. Mags are Gen2 PMAGs, if this build doesn't work with those, I'd be highly disappointed.

[eldplanko]

My guess is your malfunction is an empty case and a fresh round jammed in the action. That's the extractor releasing the spent case before it can be ejected. That's an extractor problem

Thats what's happening. Will try swapping bolts should fix this right?

[Ryno12]

Just make sure you only try one thing at a time.

[SteveL]

Thats what's happening. Will try swapping bolts should fix this right?

Potentially. If this works then you can go back to the original bolt and try a different extractor and extractor spring.

[MegademiC]

Make sure the extractor is not bent. I've seen that happen and is difficult to diagnose, at least it was on the gun I saw.

I don't see it talked about much and is easy to check so I'm just throwing it out there.