The .45 ACP

John Browning designed the Colt 1911 .45 Automatic pistol, the pistol held 7 rounds in a detachable magazine most often referred to incorrectly as a clip. The design of the weapon was simple as it reloaded itself using the energy from the exiting round, this was extremely helpful in close quartered combat.

The M1911 was used in the U.S. Military from 1911 until 1985 and is probably the most recognizable weapon in the world. The weapon gained widespread support by troops during the first World War increasing the demand and that led to the Springfield Armory manufacturing the weapon in addition to Colt.

The Colt .45 ACP was replaced by use in the U.S. Military by the Beretta 92F in 1985, the 9mm weapon was chosen for logical reasons, most of the worlds armies used 9mm ammunition and the theory was ammunition would be plentiful during any future conflicts.