I just acquired an Yugo SKS that has the grenade launcher on it. I am planning on purchasing a golf ball end for it. I know that you move the gas chamber selector to the downward position for regular shooting, but do I move it just up for grenades? or do I move it up and then back? with the gas piston in I cant move it backwards and without the gas piston it it will but then the pin falls out so I am assuming you just move the selector up to the 12 o'clock position for grenades and then down ward to the 4 o'clock for live ammo?? is this correct?