There’s some discussion about 3D printing over at The St. Louis Gun Rights Examiner. Jason and I have spent a good deal of time exploring both possibilities, since he has both a rudimentary hobbyist-grade 3D printer and an inexpensive and workbench sized CNC mill. We started off trying to print a magazine for an M11 submachine gun. One issue is that extruded ABS from a printer is a lot less rigid than the thermoplastics that are often used to make magazines, so the walls needed to be a lot thicker than on a production magazine, which reduced capacity and reliability. We still haven’t gotten around to trying to live fire a magazine.
Then Jason did an AR-15 lower receiver that uses a modified, bolt-together design to make it easier to mill than a standard lower. This actually works quite well. There’s also an M1911 in the works, but until Jason gets his Delorean back on the road again, that’s on hold.
There really isn’t a comparison between the two techniques. Hobbyist grade 3D printing is currently not up to the task of making guns, and is barely up to making plastic copies of plastic magazines. Plus, as I’ve mentioned before, one has to be careful in one’s selection of plastics to avoid legal issues when using plastics in firearms. CNC machining works fine, however, and is within reach of hobbyists. Jason is not a skilled machinist, and yet still managed to add a bit to his collection. That’s not to say that CNC milling doesn’t require any skill: it does. There’s also a good bit of trial and error that a skilled machinist would likely avoid, and aluminum isn’t cheap. The real promise of 3D printing over CNC is that 3D printing takes relatively less skill, at least in theory, but the technology is not quite developed yet, and metal 3D printed parts are still at a price point beyond that of a hobbyist.