The marker I had was perfect, with no o-ring on the bolt and the front bolt removed the gun cycled a shot and did not try to recock. I just adjusted the recock screw.
On the next gun I tried I had issues with the bolt holding the valve open after the shot. It might be best to pick a gun that already does not want to cock without liquid.
I really couldn't bring myself to cut the cat, because it was in too good a condition. I need a beater.