Re: Stumped! Chamber pressure
I had a similar problem on a NEW gun except that I had primer blow-outs all the time even on factory loads. I swore it was the chamber. I even sent it back to Savage and of course there’s never anything wrong with the rifle… they said stop loading hot rounds, even after my detailed explanation.
The comparison of those stuck cases to your other rifles does not compute, there is no corelation. Only that if you compared those other same caliber rifles’ case dimensions before and after, to your Cooper it may help give you some insight.
What headspacing are you getting, before and after dims? What dies you using? Have you tried small base dies? Is it a custom chamber?
I may if I were you, send the gun to re-ream chamber or just rebarrel and then sell it, you might make up most of the cost, I know, I know, its hassle/money, but sometimes the chamber is not reamed exactly as one would want it, and a slightly ‘bad’ chamber is just a small % of thousands to a businessman. If he can sell it, he will. Imho. ..good luck.