The Rapidly Expanding Supply of STL Files That Should Make Gun Control Advocates...

into advocates of a totalitarian society, with Internet censorship, licensing of machine tools, etc.

At GrabCad  (registration required), there are STL files available for the AR-10 lower receiver, the MAC-10 receiver, and various other interesting objects.  You can display them in a 3D viewer, and at first glance, they look right.  There are a lot of CAM programs out there that will load these STL files and machine these parts on a CNC mill.  By comparison, the rest of the parts required to complete these weapons are easy to machine on a vertical mill, with the single exception of the barrel (and those are readily available to purchase online, no serial numbers).

As CNC mill technology gets cheaper, and as 3D printers start to work with better plastics, gun control will go from a delusion to obvious fantasy.

UPDATE: For those going old school: blueprints for making a MAC-10 receiver.  Obviously, the parts will need welding to put them together.