What is the cause of a bolt getting stuck forward on a full chamber?  I've had this happen a few times with a few different setups but what is the cause of this?  I believe some people call this a "sticky bolt" or a "hard lock".  

So I've tried a few different 7.62x39 bolts and none of them seem to work correctly.  I just purchased a Liberty Gun Works bolt and it seemed to work the best out of all the ones I bought so far except there were some FTE's towards the end of my session with it.  

I decided to try my hand with the LMT bolt and while it looks awesome, I did some function checks with it using some spent cases and I found that the bolt would stick forward with a spent case in the chamber.  

Is this a head spacing issue?  

Is there any way for me to still use this bolt (IE have the bolt face taken in a thousandth or something?)

ETA: Somebody fucking help.  I've spend around the price of a full WASR-10 on 7.62x39 ar bolts and none of them have worked so far.  I thought spending $180 on a supposed proven bolt from LMT would be the answer but it doesn't seem to mate with my barrel.

1) Dirty chamber and/or new chamber.
2) Weak gas- check alignment of gas block with the hole in the barrel, size of hole, seal around gas block and gas tube.

The barrel is pretty much a virgin.  I installed it a while ago and just shot 40 rounds through it at the range with the Liberty bolt.  Hopefully that's it.

Minimum spec chamber/ maximum spec ammo.

I figured out what this was.  I was using spent brass from a Liberty Gun Works bolt which the owner stated to have loose head space.  The brass was probably stretched causing my LMT bolt to get locked shut.

At the range today with fresh cartridges it worked like an absolute champ though!

Buy Hornady's headspace gage. It will allow you to accurately measure new, resized and once fired brass and ammo.

Your fired case may not fit in the chamber regardless of which bolt you use. This especially true if it's steel cased.

Contact the barrel manufacturer and discuss your concerns. Currently there are at least two different bolt dimensions on the market for use with 7.62x39mm/6.5 Grendel case heads. They are not interchangeable. If you have the wrong bolts they'll never work. If the barrel isn't headspaced properly it will never work.

Forced closure on live ammo or the inability of the bolt  to close completely is almost always a headspace issue. Either a rifle headspace issue or an ammo headspace issue.