You say this is a pet load,which is fine to have, but I will say you should start over and work it back up in the new gun. If the bore is tighter or some other variable in the new gun, your pressures might be higher than in your old gun. I had a load I shot tons of in my S&W 629, which isn't the strongest gun in he world. Well, I figured my T/C Contender would handle it with ease. I fired 1 round, and had to remove the barrel to tap out the case. No harm done, but it taught me to not assume guns will all handle the same loads, no matter how "strong" we think they are. Try dropping back to start loads, and see if the problem goes away, and work back up if it does. I have a Hornet that will pierce primers, but only when I get carried away with the powder charge. Let us know what you find out.