What if, instead of just distributing the files to print a gun, someone sold a machine that could make one? The Ghost Gunner milling machine is a provocative attempt to answer that question. Milling machines turn metal into objects in the same way that sculptors make statues out of marble: they remove material until the finished product is all that's left. Milling is used to make a variety of tools, but as its name implies, the Ghost Gunner's main function is to make guns. That's what FedEx has a problem with, though it's a bit more complicated than that.