Earlier this month, US Customs and Border Protection agents arrested a man about to cross into Mexico from Arizona with a carload of guns and ammunition. Among the weapons was a semi-automatic rifle modified to function as an automatic - notably, the modified rifle had a 3D printed lower receiver. This is the most recent incident in which 3D printed weapons have shown up in the hands of criminals, which, worryingly, is beginning to happen more frequently. Read more at 3DPrint.com: http://3dprint.com/120891/3d-printed-assault-rifle/