The FP-45 Liberator was a cheap single-shot pistol designed by the U.S. military during the 2nd World War to serve as a disposable weapon, the idea being to "arm a million people in Europe for the cost of a single battleship." The intent was to provide ultra cheap 'insurgency weapons' which could be dropped behind enemy lines to friendly forces.
The simple design and single shot capacity would ensure that the weapon be regarded as relatively useless by any enemy military (firing a .45 ACP round from an unrifled 4-inch barrel, the weapon's effective range was around 3 yards, it got a lifespan of about 50 rounds, and the all-metal body and locked breech means the weapon can injure the shooter's hand when fired if they are not wearing gloves, and is generally incredibly unpleasant to shoot), but could be used as a last ditch defensive weapon or to seize better weapons from enemy forces, which was the weapon's primary purpose. It was made in utmost secrecy, with instructions using non-firearm terms such as "spanner" to describe the parts and a deliberately misleading designation ("FP" for "Flare Projector").
25,000 were dropped to the French resistance, 100,000 sent to China, and a few thousand airdropped in Greece, but most of the remainder produced at around a million guns were destroyed after the war.
The Liberator is a very simple single-shot weapon: while it can store 5 additional .45 ACP rounds in the grip, this is just a compartment and does not feed into the weapon. To operate it, see the video below. The production cost was an average of $2.10 per gun during that time (now $31.76 in 2018 money).
Sources: http://www.imfdb.org/wiki/FP-45_Liberator
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