Charlie,
I have some contacts at the Federal plant that I will check with first, I saved the box and hull in case they want to see it. Thanks for the tip about the lab. I didn't see any signs of over pressure in any of the other hulls. I suspect it was just a defective primer in this case. I shoot these by the case loads in trap and sporting clays in other guns without any problems, and had shot 40 or so in this gun the day it happened without any issues. Since it actually punctured the primer (it really looked like a small tear instead of a puncture hole) my main surprise was that the lock plate was sealed tight enough to the stock to generate that kind of internal pressure. I would have thought that the stock would have split before before a lock plate would have bowed.