A Personal defense weapon (PDW) is a type of semi-automatic or fully-automatic firearm similar in most respects to a submachine gun. They typically have better range and accuracy than normal submachine guns. Cartridges such as the 4.6x30mm and 5.7x28mm use specially constructed and shaped bullets, along with high velocity to provide better armor penetration than traditional 9mm Parabellum or .45 ACP rounds.