KABOOM!!! Come on in ....Seeking Advice/knowledge.

[StoneHendge]

That's happened to me. I was running a 6 Grendel warm and the barrel's chamber didn't fully support the case walls. Meaning a much larger unsupported area than normal. I had Magnetto on and velocity was about 1k fps low. Your bullet was low because half your pressure bled out the mag well. I'd check your receiver's mag well - mine bowed out a little.

I'd also drop a bullet in the chamber and compare it to how it sits in your other Grendel. I'd also be wary of using the bolt and carrier again. I retired my bolt but did try to use the carrier again. It wouldn't cycle.