Semi-automatic rifles are a type of rifle that fires a single bullet each time the trigger is pulled, automatically ejects the spent cartridge, chambers a fresh cartridge from its magazine, and is immediately ready to fire another shot. They may be operated by a number of mechanisms, all of which derive their power from the explosion of the powder in the cartridge that also fires the bullet. A semi-automatic rifle may be originally designed to be semi-automatic (such as the American M1 Garand or Russian SKS), or a civilian version of a military assault rifle design that lacks its fully-automatic fire mode. Semi-automatic rifles were first widely adopted by militaries during World War II, and briefly usurped bolt-action rifles before being replaced with select-fire automatic rifles such as