Abstract: An apparatus for opening a delivery valve in a gas reservoir chamber of a compressed gas operated gun comprises a compressed gas chamber in a cylinder and a gas reservoir chamber adjacent thereto. The gas reservoir chamber is normally closed at the side of the compressed gas chamber by a suction check valve and at the side opposite to the compressed gas chamber by a rod-like delivery valve which also closes a leading hole leading to a barrel bore. The delivery valve is slidably arranged within a through-hole which opens into the gas reservoir chamber at the side opposite to the suction check valve, and is urged by a spring so as to normally close the leading hole, and the rear end of the delivery valve is engaged by a latch lever of a trigger.