taking it apart won't help.. there are 3 o-rings on the valve. one where the valve lifts off the seat to let gas through and 2 on the body sealing. if it is leaking gas when not shooting it is either the first or second o-ring. if the rings look good could be a bent stem not seating the o-ring well or the o-ring seating surface is damaged. inspect them very closely. that snap ring should come out with a pair of pliers if i remember right.
