Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A semi-automatic pistol is a type of handgun with a single chamber and a single barrel which remain in a fixed linear orientation relative to each other while being fired, with some sort of mechanism powered by the previous shot to load a fresh cartridge into the chamber (semi-automatic operation), so that one round is fired every time the trigger is pulled. Handguns that achieve this end by using multiple chambers and a single barrel (revolvers) or multiple chambers and barrels (for example, some derringers), are not called semi-automatic pistols.