If this happens you are still in the game, unless you called out. You are automatically out when you get hit and it breaks. The entry point for paintballs into the gun. The breach sits just above the firing chamber so that paintballs can be staged with out jamming. This is used to hide behind.
Examples are natural brush, pallets, trees, or another hiding spot.
This is done more in tournament play. It is a quick move upon a bunker to eliminate a player at close range. This part can be found on a CO2 tank. If the operator overfills the tank the burst disk will rupture. You can stop the air by simply tightening the nut down.