[riskneutral]

> your average garage setup is not remotely capable of rifling a barrel

Ehhh ... you talk a lot about 3D printing, but that’s not the only tool that people have in their garages. A huge number of people have metal lathes in their garages. I happen to have a small, CNC controlled metal lathe and mill in my garage. The whole setup cost me about the same as a high quality, rapid prototyping 3D printer (<4000USD). I am pretty sure I could make a firearm, in my garage, including rifling, if I was determined to do so.

Personally I have no desire to build my own firearms, because it’s illegal to do so in my country and it’s also extremely dangerous. But in many places in the US it does appear to be legal.