Troubleshoot

[blackfoot]

I just fired my Grendel upper for the first time today and the bolt doesn't cycle. It's not that it short strokes or anything, it just plain "locks up" upon firing. I can cycle the bolt with the charging handle but it' s a a little stiff, probably normal for after firing a cartridge if the bolt doesn't cycle. Possible causes???? I've tried it on both of my lowers, one of which is another Grendel (.264 LBC).

[Mutt]

Oil it.

[blackfoot]

Wish it were that simple. It was clean and oiled. Although it was cold outside the gun was warm on all firings. I'm thinking gas block problem?

[bwaites]

3 possibilities.

1. Gas port obstructed.

2. Gas tube obstructed, or kinked.

3. Carrier key loose, or not aligned with gas tube.

[elkbow]

it locks up? locks up how? you mean it makes it partially back? thats not a gas problem, you have another problem if it is hard to cycle by hand. Ok, so if you fire it, then it tries to eject the round and makes it part of the way back and locks up??

[blackfoot]

No, locks as in acts like a bolt action and the bolt stays locked in battery. Getting it taken care of.

[LRRPF52]

Sounds like there isn't a gas circuit. Even with a loose carrier key, you will have almost normal cycling, at least in a 5.56 gun. Even if the case seized in the chamber, the bolt would be thrust to the rear by a proper gas circuit, with the extractor just slipping off the cartridge rim.

My best guess: Gas block not aligned with gas port, or gas tube not aligned with gas port. Either way, something ain't right.

[Bennybone]

Find someone with a working grendel upper, swap bolt and carriers with them. see if that other BCG works in your gun.

I recently had this happen with my 6x45mm build.

Everyone said it had to be a gas system problem but it ended up being the bcg.

BB