A personal defense weapon (PDW) is a class of compact magazine-fed, self-loading, firearm – essentially a hybrid between a submachine gun and a carbine, retaining the compact size and ammunition capacity of the former while adding the stopping power, accuracy and penetration of the latter. Most PDWs fire a small-caliber, high-velocity bottleneck cartridge, resembling a small or short rifle round. This gives the PDW better range, accuracy and armor-penetrating capability than submachine guns, which fire pistol-caliber cartridges.