Guns: 3D Printable AR Magazine

crank posted a neat DIY project - a 5-round AR-15 magazine that you can craft at home with a 3D printer:

AR mags are well and good, but I doubt you're going to use your fancy 3D printer to crank out something you can buy at Gander Mountain. No, where I think this kind of tech will find real popularity is the creation of magazines and parts for obscure, antique firearms - a mag for the Polish Army's self-loading 1938M carbine might be difficult to find in Ye Olde Gun Store, but it only takes one guy to upload the printing plans on the Web...