Who would have thought it? Printing guns is frowned upon. Even in the US.
Cody Wilson, a law student at the University of Texas at Austin, found this out last week when Stratasys , the company that made the uPrint SE 3D printer he was leasing, got wind of his plans to design a 3D-printable  handgun and took back their equipment.
"The company is less than thrilled with what we're doing. They're trying to prevent me from breaking any laws with their product," Wilson told New Scientist. With several friends, he has founded a group called Defense Distributed  to promote ideas about universal gun ownership.
If you build it&
In a letter to Wilson, lawyers for Stratasys cited his lack of a federal firearms manufacturer's licence  as their reason for the repossession, adding that it does not knowingly allow its printers to be used for illegal purposes. Wilson countered that his group's aim is to disseminate a printable gun design online, not print guns per se.
Stratasys wasn't buying that, and with good reason: Defense Distributed's stated aims include the building of two prototypes of differing complexity that can be printed on a uPrint SE. If the guns work, the group will modify the designs for use on entry-level 3D printers like RepRap , which cost less than £1000.
So far, the plans are limited to computer-drawn designs no physical prototype exists. But if Wilson and company manage to build the first fully printable gun, they will risk more than just running afoul of the law. Bullet propellants can create temperatures of up to 1000 °C . The powdered nylon that entry-level 3D printers use for construction, called ABS, cannot cope with that.
"The gunpowder explosion will probably be too much for ABS and other plastics in low-end printers," says Stuart Offer of 3D-printing firm 3T RPD  in Newbury, UK. In all likelihood the gun would be destroyed, perhaps even blowing up in the shooter's hands, after firing no more than a few rounds.
Fire when ready
3D printers exist that fuse metal powders using laser or electron beams to produce sturdy, solid objects. But those machines cost around £500,000, says Offer, who uses them to make driver roll hoops for Formula 1 cars. And assembling a gun isn't like snapping together Lego pieces each part must fit and move precisely.
3D printers that fuse metal could make gun components, but those parts would not make ready-to-fire guns, says Dan Johns, an additive-manufacturing engineer based in Bristol, UK. "The parts would need final, expert machining."
Still, as prices for more sophisticated printers fall, printing functional weapons is likely to become an affordable prospect. When that happens, governments will be faced with a decision. Could they lean on internet service providers to seek out and delete gun design files as they circulate online, as some ISPs are now asked to police music and movie file-sharing?
That wouldn't work, says Wilson: "We know that such efforts will be totally futile, with only random and disproportionate enforcement."
Another possibility would be to more tightly regulate ammunition, as a few US states have done , so that shooters must get a license before they can purchase bullets. But Wilson sees a way around even this: print your own ammo. If the gun project has even modest initial success, he says he expects to get working on this too. "3D printable ammunition would be a joy to pursue."