I am surprised no one has suggested this, because I have mentioned this issue to various smiths in the past and the immediate question was if the gun was off-face at all, the implication being that if it was, it could allow the primer to "flow" back around the firing pin. I'm interested in anyones thoughts on this.
More recently my own gun was sticking this way with federal primers to the point that it was piercing a few and the firing pin was distorting the primers on others, but I have no issue with winchester, cheddite or CCI primers on similar-pressure/payload reloads (7/8oz 12ga +/- 7000 to 7500psi), same hulls, etc. The gun sticks to the point that I have to knock my hand against the bottom of the hinge to open it with the federals, opens easy as can be with any other brand. Note the drag marks on all of the federal primers.
