@MinistryOfTruth have you tried any ammo from a completely different batch lot#?
could be Hornady had a small run of oversized primer pockets that were just enough to blow out with the internal ballistics of 6.5CM. I know that was a contributing factor to the issues with the 6.5CM SCAR
other thing you might inspect is how close your chamber is to minimum spec, kissing it gently with a fractionally larger reamer might give the case enough room to do its thing without popping the primer.
could be Hornady had a small run of oversized primer pockets that were just enough to blow out with the internal ballistics of 6.5CM. I know that was a contributing factor to the issues with the 6.5CM SCAR
other thing you might inspect is how close your chamber is to minimum spec, kissing it gently with a fractionally larger reamer might give the case enough room to do its thing without popping the primer.