About 20 years ago a friend bought a box of Charles Dalley marked 20 Gauge field loads to shoot trap with in his Ithaca 37. The first shot locked up the slide. I don't recall how he got the shell out of it. He returned the shells to the dealer for his money back. I still have the shell. The primer is very flat. The rim flowed into the exstractor cut and all around its circumfrance in the rim cut into the barrel. Gas marks show on the skives where the plastic comes out of the brass. This was a factory shell and definately was making more than proof pressure. The gun was still useable. I don't know if there was any dimensional damage to the lock up. Hats off to Ithaca for such a strong light gun. I shot an apparent overload out of an Ithaca SKB Mod 200E Skeet gun. I remember shooting at high 2 with a terrific recoil. The gun opened up. I thought it came appart in my hands. The stock cracked at the head. Later on the fore end lug got loose and I sent it back to SKB in Japan to have it resoldered. I load my 12 Ga shells on a PW press that I have owned since 1984. That is the only shell that I ever had an overload problem with. I don't know how or what caused it. I cannot believe it was the press. I've loaded I don't know how many 10's of thousands of rounds on it and love it. The odd thing is that the empty shell(old AA) was not deformed in any way. Maybe we blame ourselves for these things. Most often it is our fault. But can the factory be the blame sometimes? Is it possible that Joe the primer maker can make a mistake? How about 2 primer pellets in one battery cup. I don't know if it's possible but would think that could raise some hell in a shot shell. I know that more powder or shot in a shot shell gets noticable fast when it won't crimp right or close at all. What would a live primer do if loaded into a shotshell? It does not matter what loader you have. Sometimes I have live primers fall off my loading table. They mostly land on the floor. But I keep my empty shells in target boxes near the loader. If one were to fall into one of my empties that was about to get loaded maybe that is how one could get into a loaded shell. Maybe that is what happened to my 200E. I guess a little house keeping is in order.
