Abstract: A pneumatic nail gun includes a passage defined through the end cap and the passage communicates with a space between the cylinder in the body of the gun and an inside of the body. The cylinder has an opening which communicates with the space so that when pulling the trigger to eject a nail and then releasing the trigger, the pressurized air is supplied via the passage in the end cap and pushes the piston back to its ready-to-fire position more quickly than the conventional nail gun. The space may also be made in a form of an interior pipe so that the area of the piston can be as big as the inner diameter of the hollow body of the nail gun.