<Li> 100 - round drum magazine </Li> <P> The Thompson submachine gun is an American submachine gun, invented by John T. Thompson in 1918, that became infamous during the Prohibition era, becoming a signature weapon of various police syndicates in the United States . It was a common sight in the media of the time, being used by both law enforcement officers and criminals . The Thompson submachine gun was also known informally as the "Tommy Gun", "Annihilator", "Chicago Typewriter", "Chicago Piano", "Chicago Style", "Chicago Organ Grinder", "Trench Broom", "Trench Sweeper", "The Chopper", and simply "The Thompson". </P> <P> The Thompson was favored by soldiers, criminals, police, and civilians alike for its large . 45 ACP cartridge, accuracy, and high volume of fully automatic fire . It has since gained popularity among civilian collectors for its historical significance . It has had, and continues to have, considerable significance in popular culture, especially in works about the U.S.'s Prohibition era and World War II, and hence is among the best - known firearms in history . Although the original fully automatic Thompsons are no longer produced, numerous semi-automatic civilian versions are still being manufactured by Auto - Ordnance . These retain a similar appearance to the original models, but they have various modifications in order to comply with US firearm laws . </P> <P> The Thompson Submachine Gun was developed by General John T. Thompson, who originally envisioned an "auto rifle" (semi-automatic rifle) to replace the bolt action service rifles then in use . While searching for a way to allow such a weapon to operate safely without the complexity of a recoil or gas operated mechanism, Thompson came across a patent issued to John Bell Blish in 1915 based on adhesion of inclined metal surfaces under pressure . Thompson found a financial backer, Thomas F. Ryan, and started the Auto - Ordnance Company in 1916 for the purpose of developing his "auto rifle". It was primarily developed in Cleveland, Ohio . The principal designers were Theodore H. Eickhoff, Oscar V. Payne, and George E. Goll . By late 1917, the limits of the Blish Principle were discovered: rather than working as a locked breech, it functioned as a friction - delayed blowback action . It was found that the only cartridge currently in U.S. service suitable for use with the lock was the . 45 ACP round . Thompson then envisioned a "one - man, hand - held machine gun" in . 45 ACP as a "trench broom" for use in the ongoing trench warfare of World War I. Payne designed the gun itself and its stick and drum magazines . The project was then titled "Annihilator I" and by 1918, most of the design issues had been resolved . However, the war ended two days before prototypes could be shipped to Europe . </P>

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