[doe_eyes]

You can't easily make a high-quality firearm a hobby mill, chiefly because the barrel needs to be made out of good steel and needs to be rifled. But the quirk in the US is that federally, only the receiver is the regulated part, and many types of receivers can be made out of plastic or aluminum. You can certainly use cheap three-axis CNC with some fixturing to make AR-15 receivers, for example, and many people did. Cody Wilson / Defense Distributed had this whole thing where they were selling CNC mills for cranking out guns.

You can also definitely make junk single-use guns using either technology, just like the 3D-printable "Liberator".