AI AT-X bolt cycle issue…

[Nostradumbass]

Hey fellas,

I’m running a Gen 1 AT-X, and currently have over 2k rounds through the action.
Until just recently, I’ve used the 6.5CM factory barrel. I have since switched to a 308 barrel.

I’m running a light charge 308 loading, and I’m having my bolt stick at the very last part of the cycle. The last stroke of the bolt cycle where the cocking lever disengages with the trigger assembly (forgive my ignorance if I have the nomenclature incorrect.)

What I’m saying is, there are no signs of pressure on the brass, the bolt lifts perfectly fine and easy until the very last bit, and I have to lift it hard to get it to release….I’ve cleaned the chamber and made sure I have no lube on my brass, but the bolt still does this sticking action almost every cycle….sometimes it works just fine though.

Any thoughts? I’d appreciate a fresh set of brains to help me make sure I’m not missing something.

I will say that my brass is older and likely in need of replacing. I plan to shoot some factory ammunition today to see if it replicates.

Thanks boys!!!

 

[clefairy]

Old brass expanding a lot is my guess. Running different 308 rounds will verify.

 

[Supersubes]

Check the base dimension of the brass, thats where your interference is. Your die isn't sizing enough in that area.

 

[Nostradumbass]

Check the base dimension of the brass, thats where your interference is. Your die isn't sizing enough in that area.

I checked, and OD is .4695”.
Spec from what I’ve found is .470”
I’ll check the other case dimensions again.

 

[Supersubes]

I checked, and OD is .4695”.
Spec from what I’ve found is .470”
I’ll check the other case dimensions again.

Spec is actually bigger than that, or it should be anyway. No matter, when the bolt lifts normally, and then sticks on the extractor can, the case is fat at the base.

My personal .308 AI barrel (original AI factory barrel) is very tight in that area too.

 

[Nostradumbass]

Spec is actually bigger than that, or it should be anyway. No matter, when the bolt lifts normally, and then sticks on the extractor can, the case is fat at the base.

My personal .308 AI barrel (original AI factory barrel) is very tight in that area too.

Well, I was able to diagnose the issue. The problem is with my brass I’m using to reload with. It’s older Lake City Match brass, which is likely not the best brass anyway. Factory Federal GM Match ammunition fed flawlessly with the action being butter smooth through the cycle.