lol, ive had plenty of practice with my air rifle, and im 6'3" and work outdoors, but it does make my arms shake if i dont keep it topped up. im not sure of the exact size of my rifles tank but its gonna be about the same size, and im hoping paintballs use less gas but i guess i cant fire 15 bps with the air rifle. will keep you posted on just how effective/painfull it is. on the plus side ive got 3 tanks so i guess i can just keep changing them. how many shots could i expect from 68ci and how big is that in cc? do you just multiply it by 2.5? p.s. ive got a post in the newbie section i could do with some help on, i didnt give it a good description, and am not getting as much help as i am from you guys. congrats skeetmaster, how many is than now?