Did you know that it's perfectly legal to make your own modern, cartridge firing firearms? Here's what the BATF has to say about it, from their FAQ page:
With certain exceptions a firearm may be made by a non-licensee provided it is not for sale and the maker is not prohibited from possessing firearms. However, a person is prohibited from assembling a non-sporting semi-automatic rifle or non-sporting shotgun from imported parts. In addition, the making of an NFA firearm requires a tax payment and approval by ATF. An application to make a machine gun will not be approved unless documentation is submitted showing that the firearm is being made for a Federal or State agency.Some thirty or more years ago there were a series of small ads in the classified sections of Popular Mechanics and similar magazines offering plans for the home gunsmith from an outfit that went by the acronym JACO. Most were simple, single shot pistols, like the one displayed above, and the sellers stated that all could be made with no more tools than a hacksaw, files, and a drill. Today, I see that a number of websites have resurrected these plans, and at least one enterprising soul has been selling them on eBay!
To make it even easier, JACO also sold plans for a filing fixture that was clamped over the workpiece, and used hardened steel rollers to guide a file. The claim was that with this fixture it was possible to get the kind of accuracy you'd otherwise need a milling machine to obtain- although of course it would take longer with the fixture. I don't doubt it. Such fixtures were more common in earlier centuries, and I seem to recall that Guy Lautard had a design for one in one of his Machinist's Bedside Reader books.
While the Federal laws on constructing firearms are no hindrance to this sort of project, state laws may be. Here in Michigan, handguns must be registered with the state, and only a gun already registered to a licensed dealer or another individual may be transferred. I'm not sure how this affects home made guns, though I'm tempted to drop a line to the State Police for clarification. If your state laws do permit this sort of thing, it does look like a great hobby project for the shooter with patience and an aptitude for craft.
UPDATE: Here's a complete PDF, with instructions, of the JACO mini pistol plans. (link fixed!)
UPDATE: Some creative Google searching indicates a number of patent applications- but no patents granted- to a John Kasselman and Albert Blatter (hence the name JACO) for a filing fixture, three pistol designs, and a method for bluing steel.
UPDATE: Two more Jaco pistols: the JACO Western Pistol and the JACO Derringer.
Ambitious home gunsmiths can find a wealth of info and a clever design in The Handgun. Home gunsmiths with access to a lathe and the willingness to navigate the complex applications needed to legally make automatic weapons will find The Do-it-Yourself Submachine Gun both interesting and useful.
(Less well equipped hobbyists looking for fun projects will find Backyard Ballistics: Build Potato Cannons, Paper Match Rockets, Cincinnati Fire Kites, Tennis Ball Mortars, and More Dynamite Devices a great source of entertainment.)
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