[myfriendis410]

If it's manufactured after the turn of the century it's a fluid steel barrel and designed for smokeless. You will be able to tell in a hurry if it's a 2 1/2" chamber when you shoot the longer shell it should drastically fray the end of the hull. My guess though is it's a 2 3/4" chamber designed to shoot a paper hull. You might want to have the forcing cone lengthened to take the plastic shells.