This cartel group didn't bother with the "Ghost Gunner", which is a joke. They got a real Hardinge 3-axis CNC mill and made parts from solid aluminum blocks. Hardinge is an old-line US machine tool builder, in business for over a century.
There's stuff in the article about "where did they get the G-code" to cut the part. Any good CNC machinist, given measuring tools and a part, can model a part like that. It helps if you have SolidWorks or Autodesk Inventor.
Or you can just look up "lower receiver 3D model" and download the model from GrabCAD.[1]
Maybe gun serialization should include barrels. Good rifled barrels are hard to make, and require special purpose machinery.
The best rifle barrels are probably hammer forged, and indeed that requires $$$ machinery and tooling, but I'm under the impression that button rifled barrels aren't that hard to make.
But certainly a lot more than AR-15 pattern lower receivers, which are not highly stressed by firing (here's a 3D printed plastic AR-10 pattern lower receiver! http://3dprint.com/54163/printedfirearm-ar10-piece/), you need good steel, a big lathe at minimum and I'm pretty sure heat treating is a good idea.
Any proposal to serialize barrels would be shot down, so to speak, in the US now and for the foreseeable future.
Certainly, for manufacturing purposes, you frequently want to do that, especially for guns like the Glock where all three of those are relatively easily swapped. But making it a legal requirement would be another thing altogether; heck, in the US gun serial numbers preceded legal requirements by more than a century, it's only been required since 1968 as far as I know.
Hmmm, there's also the other sort of legal requirement, dealing with lawsuits. Glock doesn't want to have liability for a FrankenGlock kaboom....
Kind of off-topic, but one avenue where serial numbers stamped on all major bits have been useful is to collectors. I've seen a few that Forgotten Weapons covered that went for a pretty penny at auction because everything had matching serial numbers...
But that's a really good point about liability since there's so many after-market replacement barrels for Glocks. Heck, I've been tempted at times to get one just for the standard rifling (and I don't shoot lead).
Many firearms, Glocks by way of example have serialized barrels. The issue is, sticking with the Glock example, that the polymer lower carries the serial plate and is considered to be "the firearm" since barrels are interchangeable and their sale is not regulated. It is straightforward to get a replacement barrel. Barrels do not have an infinite service life and barrel replacement is not uncommon.
There's stuff in the article about "where did they get the G-code" to cut the part. Any good CNC machinist, given measuring tools and a part, can model a part like that. It helps if you have SolidWorks or Autodesk Inventor.
Or you can just look up "lower receiver 3D model" and download the model from GrabCAD.[1]
Maybe gun serialization should include barrels. Good rifled barrels are hard to make, and require special purpose machinery.
[1] https://grabcad.com/library/ar15-lower-solidworks-native-1