I'm using my 20ga. CZ Bobwhite side by side in Cowboy Action shooting. On my first stage Saturday, I had fired both barrels and then discovered that the gun wouldn't break open for the last two shots of the stage. On closer inspection, I was able to "break open" the action by bringing the gun down on my knee. The primer on the shell coming out of the right barrel appeared to be punctured. I continued to experience this problem all the way through the match, having to break it over my knee, and each time at least one of the shells appeared to have the punctured primer. Is this an ammo problem, is my firing pin(s) too long? Ammo is factory Winchester AA skeet loads/9 shot.