premature case head seperation

[timelinex]

I'm posting this for my friend, since he doesn't come on here too often.

He has a 338 AIAW and out of what seems to be nowhere, he is starting to get case head separation after the first shots. So the first time he fires his round, the brass has a big bulge in the case head area, and then by the second time it either busts and gets stuck in the rifle or its just barely hanging on there and would bust next time.

His load is not too hot and he's using lapua brass. Nothing has changed.

He sent his dies into redding to check if that was the problem and it wasn't. He has double checked his charges. he has made sure the chamber and barrel are squeaky clean.

Unless the case ruptures, his accuracy is the same and his POI's haven't changed.

Any ideas on what he should be checking next?

 

[HodgdonExtreme]

Pictures and ammo details, please.

 

[918v]

Is the action in good working order?

 

[timelinex]

I'll try to drag him on here and get him to post pictures..


Action seems to be working..? The bolt goes down, everything fires, and running the bolt extracts the brass and resets the trigger. Maybe I'm not sure what your asking about the action.

Ammo is something like :

91 gr retumbo
300gr bergers
lapua brass

He's done all the measuring involved to confirm that the brass is to spec and is being sized correctly. He's also confirmed the charges on a scientific scale.

 

[918v]

Maybe it cracked or he sheared a lug off the bolt.

 

[Temp9]

Bulge above the case head tells me unsupported chamber. That would surprise me in a factory AW, though. Pictures will give us a better idea of what's going on.

 

[Sniper Uncle]

Interesting. I thought AI's never fail....

 

[jdonovan]

has a big bulge in the case head area

can't happen if the chamber doesn't have a defect, and the bolt is keeping the back of the chamber sealed.

define "big" .002 .020 ? pictures might help.

Is the bulge uniform around the head of the case, or only on part of the cartridge?

If non-uniform, can he attribute it to a consistent orientation in the chamber?

 

[BuzzBoss915]

I would stop shooting this rifle and have it evaluated by a competent gunsmith. bb