US Patent 7712465 Valve for gas operated gun

In a paintball gun 10 the valve member 17 which controls communication between the gas canister 13 and the barrel 11 of the gun is balanced by a piston 23. When the chamber 21 is pressurized the piston 23 helps to unseat the valve member 17 when the latter is struck by a hammer 15, thus reducing recoil and permitting use of lighter, less robust materials.