Back in early October, the "Wiki Weapon" project, the work of the Defense Distributed group, received a fair amount of press. The goal of the project is to design a functioning firearm that can be manufactured entirely on a consumer grade 3-D printer. This design would then be made freely available on the internet, eventually rendering any notion of a "government monopoly on force" nothing more than an evil fantasy of tyranny enabling (and genocide enabling) forcible citizen disarmament advocates like the Coalition to Stop Gun Violence.
St. Louis Gun Rights Examiner has been following this exciting project with interest, and following CSGV's rising panic about it with more than a little glee. CSGV's executive director, Josh Horwitz, in fact, wrote about these developments in a hysterical op-ed column in the Huffington Post. That Horwitz piece, by the way, immediately preceded one in which he shrilly decried the possibility (as raised by St. Louis Gun Rights Examiner) of private citizens improvising explosive weapons. In both cases, Horwitz is displaying his terror of a citizenry that can simply bypass all "weapon control" laws, thus empowering the people to effectively resist an out of control government.
Since then, Defense Distributed has experimented with a considerably less ambitious version of the project, "printing" only the lower receiver of an AR-15 rifle, and assembling the rest from commercially available parts. This is still quite significant from the political/legal standpoint, because the lower receiver is itself the part considered to be the "gun," and is thus the only part subject to all the legal hoops the government imposes on exercise of the right that shall not be infringed.
This approach was successfully implemented last summer, but for a gun chambered only for the relatively low-powered .22 rimfire cartridge. Defense Distributed upped the ante considerably, assembling a firearm chambered for the FN 5.7x28mm cartridge, so demonized by anti-gun groups for its supposed "cop killer" powers.