Chamber issue?

[koden]

I have a new Grendel I am troubleshooting. The pic below shows 5 cases that were fired in my rifle. The rounds were factory 123 Amax rounds. The round in the middle has a noticeably larger bulge by the case head. It measures 0.4405" where the other 4 measure 0.4385" to 0.4395". I have 2 sets of Hornady dies and neither will resize that round without having to bump the shoulder back too far causing headspace issues.



It is a 264LBC Type 2 chamber with a Type 2 bolt (verified bolt face depth to ensure it's the proper bolt). I tried a type 1 bolt and the bolt would not close on factory ammo.

I am not sure why it would only do this on one out of 5 rounds.

The primers show no signs of pressure.

[sneaky one]

Contact the co. from which you purchased it from-it is not sounding like a grr chamber. Was it from AA?=-CSS-JT? It could be from a bad batch of factory loaded ammo- I had some from AA in 2008-(this is why we Roll Our Own!) Find the flaw/help out the rest of the gang=thanks.