Help diagnose a .308 Win problem

[edwardware]

. . . had 2 out of 5 primers backing out. The other 3 cartridges had flat primers that were just starting to flow around the firing pin indentation.

In my experience, excessive shoulder setback leading to unseated primers will look exactly like excess pressure primer flow once you get just enough pressure to stretch the brass and reseat the head over the primer.

I agree, you're oversizing the brass.

 

[Steve Donlon]

Perhaps check to see if you are under sizing your brass, (bumping the shoulder to far back). Just offering suggestion while we wait on the experts to show up.

Good call, I did the same thing when I first started to reload my 30-06 but not only did I bump the shoulder back to far I also tried to make a reduced load with 4198 at the same time which pushed the shoulder even further back. Not a good thing. I have read that if the shoulder is pushed back to far that case separation can happen with full power loads.