A self-regulating valve assembly for a compressed gas gun includes a valve housing and a valve body disposed within the valve housing. The rearward end of the valve body defined an outlet port. The forward end of the valve body defines a gas balance reservoir open to and in communication with the breech of the gun. A valve gas passage is provided between the valve body and the valve housing, the valve gas passage providing communication between the outlet port of the valve body and the gas balance reservoir of the valve body. A slidable valve poppet is disposed within the valve body and includes a sensing end adjacent to and at least partially within the gas balance reservoir, the sensing end having a sensing face adapted to react to gas pressure within the gas balance reservoir. The valve poppet is slidable between a closed position and an open position. A valve spring within the valve body biases the valve poppet toward the closed position. Pressure in the gas balance reservoir exerts a force on the sensing face to urge the valve poppet toward the closed position.