I'm guessing that you guys getting full penetration on shells aren't shooting 50-to-80-lb-plus southern Alligator Snappers. They've found hundred-lb snappers with musket balls and bullets imbedded in the shell. No lie. Not sure who "they" are, though.
By the way, big snappers taste GREAT. Chunk them up, soak them in saltwater, batter them and fry 'em! better than chick-fil-a nuggets. Clean them first, though, as described above.
Also, big snappers are A LOT faster than you'd think- just like gators (yes, I do live in Carolina, but I have run into big gators in South Fla. everglades- and I can vouch for them being lightning-quick).
-Charlie