At-home 3D printing is on the rise, and what was once just a lofty promise is now a reality. More and more hobbyists are acquiring affordable printers, such as the Makerbot Replicator 2 and the RapMan Universal 3D (single/dual head) printer, to manufacture just about everything from toys to working clocks. Some hobbyists have used these printers for fast-prototyping items that are controversial -- or even deadly. It comes as no surprise that some would attempt to replicate weapons systems (or at least parts of them) in an effort to create a fully functional gun. It's not exactly clear who...