Abstract: A kit for converting a pump-action type compressed gas gun to a semi-automatic type compressed gas gun without having to change or modify an internal action of the gun and without requiring any material alterations to existing components on the gun. The kit is removably connected to the gun so that the converted semi-automatic version of the gun can readily be returned to its original pump-action type configuration and mode of operation. When the kit is used to convert the pump-action type gun to a semi-automatic type gun, the only component from the pump action type gun that is not used is the pump handle. In a preferred form of the invention, the kit includes an actuating mechanism, a gas distributing mechanism, and a activating mechanism. All the mechanisms comprising the kit of the invention are removably connected to the gun thereby allowing the gun to be returned to its original configuration and mode of operation.