There are some figures around here in the PPS section on this but I can't remember the numbers. Suffice it to say you won't like a 12g nasty unless you love changing 12ies. My nasty typhoon is pretty good on a 20oz and does go through it quicker than a single barrel gun for sure, but the efficiency isn't horrible. I think HurtCow posted some numbers awhile back on shot counts. Take a search and see what ye find.