Sport45
Member
I can attest to the fact that primers back out and that firing pin strikes and the piston action of the primer going off sets the shoulder back. I used to make "gallery" loads for my 7.7 Arisaka when my sons were much younger. A cast bullet over 3-4 grains of fast powder. Cases that started out properly sized for the chamber would shorten enough after 5 or 6 firings that the primer would protrude about halfway from the pocket. At that point I'd mash them and toss them in the scrap pile.
