An amateur gunsmith, operating under the handle of "HaveBlue" (incidentally, "Have Blue" is the codename that was used for the prototype stealth fighter that became the Lockheed F-117), announced recently in online forums that he had successfully printed a serviceable .22 caliber pistol.The only limitations for the spread of this are lack of technical skill, awareness of the technology and the availability of ammunition. The first two will be solved by the simple spread of 3D printing technology, which is going to spread steadily into the home and work environment (my employers, market researchers all, are toying with buying one for prototype demos). The problem of ammunition will be quickly solved by innovating alternate deliver systems. Plastic rather than metal bullets, gas fired, or electrically fired, would both solve.
Despite predictions of disaster, the pistol worked. It successfully fired 200 rounds in testing.
HaveBlue then decided to push the limits of what was possible and use his printer to make an AR-15 rifle. To do this, he downloaded plans for an AR-15 in the Solidworks file format from a site called CNCGunsmith.com. After some small modifications to the design, he fed about $30 of ABS plastic feedstock into his late-model Stratasys printer. The result was a functional AR-15 rifle. Early testing shows that it works, although it still has some minor feed and extraction problems to be worked out.
While there are still some details to sort out, it's pretty clear that making weapons at home using 3-D printers from commonly available materials is going to become much more commonplace in the near future. In fact, as 3-D printing technology matures, materials feedstock improves, and designs for weapons proliferate, we might soon see the day when nearly everyone will be able to print the weapons of their choice in the numbers they desire, all within the privacy of their own homes.
This assumes of course that 3D printers will only stick with copies of existing guns, which seems vanishingly unlikely. Innovation will occur. And the only people discussing the rights and wrongs of this technology are the curators at Thingiverse. Ponder on that for a bit.