A paintball gun having a quick-removal assembly for readily removing a pneumatic assembly from a chamber of the paintball gun body preferably includes a lift cap hingedly connected to an end of the pneumatic mechanism. A lift pin is preferably connected to the lift cap and removably engaged within a pin receptacle of the paintball gun body. Lifting of the lift cap preferably withdraws the lift pin from the pin receptacle and enables the pneumatic assembly to be removed from the paintball gun. A self-venting mechanism can also be provided to safely release compressed gas stored in the pneumatic assembly from the paintball gun during removal of the pneumatic assembly. A latching mechanism can latch the lift cap in a forward and closed position until a user desires to remove the assembly from the paintball gun. Slots can be arranged in the lift cap to permit rearward movement of the lift cap and to cause the lift cap to move away from a body of the paintball gun to allow rotational movement of the lift cap about a hinged axis.