You’re right - there’s no “need” for 3D printing. I could turn out guns from truck axles that work quite nicely.
But I couldn’t do it *quickly*. A small shop with a lathe, mill, deep hole drilling expertise, etc... might be able to (if the plan is very simple, like a Rem700) make a rifle start to finish in a man-week per rifle. Even if I broadcast the plans and BOM far and wide, I’d have to assume that, to make firearms the “old school” way, you’d have someone with some machine tools and some skill to make guns from plans I might lay out in detail.
If Uncle Sugar wanted to shut this activity down, they could snatch up guys like me by the 100’s and be done with it. Most people don’t know how to run machine tools and they’re not about to learn how any time soon, much less devote the space in their garage or shop to thousands of pounds of precision iron. There’s only eight gunsmithing schools in the nation (that I know of), and perhaps only three where someone coming out really has the chops to build a rifle/pistol from scratch. These classes are full beyond their capacity, but that’s only about a dozen guys per semester per school that are coming out of each of these programs. In other words, the net total of new gunsmiths per year who have the chops to build a rifle from scratch might be 100, schools and apprenticeships taken together. The real trick is the deep hole drilling of the hole in the barrel. Everything else is pretty easy.
Add in a dozen more machine tool technology programs at community colleges and you can shut down an illicit gun business that can produce serious guns (not zip guns, but guns capable to take a head shot at 300 yards) without appearing any more stupid or draconian than what we see today in the rampantly stupid “war on drugs.”
But a 3D printer? Feh. Any one of these hacker-type twerps can run a 3D printer. There’s hundreds of thousand of hacker-types who can run a 3D printer. There’s 10’s of thousands more every year. DefCon used to be small and “cool,” and now it’s like some huge hacker “Us” festival.
If I’m putting together a 3D printed gun, I can ship the CNC program over the ‘net to... everywhere in an hour. The 3D “ink” will likely be controlled in distribution, but that will win about as well as the controls on prescription narcotics and fertilizers - in other words, the Feds won’t be able to control it worth a damn. Kids will be able to score a barrel of 3D/MIM goo with no great feat. With 3D printing, the cat is out of the bag in a way that even dipstick liberal arts majors scribbling for major east coast newspapers can finally realize... because the technology is so simple, even a dipstick liberal arts major can run it and make a 1911 on their desk, from the same computer that is used to author their idiotic screeds.
At most, they might need a heat treat oven. OK, so that’ll be about another $1300, and they’ll need to wait a few hours. Ovens have programmable controllers now too. The instructions can be as simple as “put in the part, press ‘go’ on the oven controller.” The stooge running the oven won’t need to know jack about heat treatment. Just use an air quenched metal and give them a pair of tongs to pull it out of the oven. Done deal.
I have thought along these lines as well, but an insurgency does not need very many rifles that can make head shots at 300 yards, and they are one of the most common and least likely to be controlled items in the U.S. citizen arsenal.
An insurgency, I suspect, can use a lot more pistols and sub-machine guns. Those can be assembled rather cheaply and quickly with a lot less knowledge than you possess.
Still, it is rather an academic discussion, because the U.S. civilian supply of rifles, shotguns, and pistols is enough to meet the insurgency demands for the foreseeable future.
We have won the debate on an armed population. Now we need to win the war to uphold the Constitution.
The Second Amendment serves as a clear guide to differentiate between those who wish to follow their oath of office, and those who disdain the restraints of the Constitution.