Submachine guns are small, portable machine guns intended for use at close range. The first submachine gun was made by Hugo Schmeisser, a German firearm designer, toward the end of World War I. He experimented with semiautomatic pistols, which fired rounds at lower velocities than standard guns. His weapon, the MP1918, had an 8-inch (20.32cm) barrel and fired 9mm rounds, which were originally used in pistols. The MP 1918 operated using blowback, a simple system during which spent cartridge cases were blown backward out of the chamber due to the gases created when the weapon was fired. This action forced the bolt back against a spring and tripped the mechanism that ejected the old cartridge. After the gases dissipated, the spring pressed the bolt forward as a new cartridge was introduced to the chamber. This cycle continued as long as the trigger was held. Schmeisser used a...