Liberator: The US Army's Zip Gun

The FP-45 Liberator was a single-shot .45 pistol of dubious quality that was manufactured during World War II. They were dropped over areas that Germany occupied to aid the resistance. They could be freely dropped because they would be valuable to resistance groups and totally worthless to German troops. FP-45's had tiny barrels and mechanisms simpler and more easily made than a Derringer. They had to be reloaded via the use of a wooden dowel, making them (at the height of their production) the only gun that could be manufactured faster than it could be reloaded. They were also fantastically loud because of their tiny barrels and complete lack of silencing equipment. Each pistol held six .45 ACP rounds inside its grip but not in any kind of magazine. 

A gun like this seems like it might not be useful to anyone, but it was manufactured according to a specific philosophy. First, these guns could be mass-produced with limited resources, both in terms of raw materials and machining. Second, they're small and very concealable, both on a person and in bulk. They need no cleaning equipment, accessories, or holsters, and so many can be stored or moved in a small space. They have a simple trigger guard and fit easily in a pocket. Because of their utter lack of accuracy, they can be fired from a pocket as well as from a sighted position. Their short range renders them worthless as traditional guns, but makes them the finest of single-attack melee weapons, like a really cheap ballistic knife. They're made with the idea that they can be used to kill a better-armed person and take his weapon.

SPECIAL UPDATE: Actual machining plans are availiable on the internet for this gun. They are not hosted here. After reviewing it, we can tell you that this thing has a shitton of parts that are not particularly easy to put together.

Here's the closest thing to a technical drawing that we could come up with

Here's a little comic of how to reload it

Akimbo liberators for HARDCORE CHOW YUN-FAT ACTION

Some other pictures or something