A few automatic weapons patented in the United States in the 1820s and 1830s were called organ or machine guns, consisting of multi-barreled weapons loaded on carts. These bear little resemblance to today's machine gun, which fires a continuous stream of projectiles as long as the trigger is depressed. One of these earlier models was invented by John W. Cochrane in 1834--apparently to no great success. Richard Jordan Gatling, an American inventor and the pioneer of machine guns, invented the hand-cranked, six-barreled Gatling gun in 1862. Rotating around an axis and firing.58-caliber brass cartridges, the gun, which fed ammunition from a top-mounted hopper, made its military debut at Butler's siege of Petersburg, Virginia, during the Civil War; the ten-barrel model, firing a thousand rounds per minute and covering a range of 2,400 yards, was a deciding factor in the 1898 outcome of the battle of Santiago, Cuba, during...