I have this proble with both of my MarkIIVT in .308 and .243. I have found that the way I have my dies (RCBS .308 and Hornady .243) That work on the bras sho from my rifles or new brass. If someone brings me brass from the range, I have to do the FL resizing with the camover with the smallest trim to length dimension. It is probably from the other brass without seeing the problem in person. I really doubt that it is the gun or your dies. Spend a little money on new brass. It gave me more confidence on reloading and troubleshooting my reloading problems. And the last bit of advice, find a buddy who reloads too.

Burn more powder!

Dana