Guns are made out of less and less metal these days. High-quality plastics tend to be cheaper to use, lighter, and more durable. You can’t make every part out of plastic but you can get pretty close. Like an anonymous gunsmith called HaveBlue just did, printing out most of an AR-15 rifle.
Using CNC and 3D printing technologies in gunsmithing has been around for a while. Obviously the military has a lot of interest in a system that can churn out cheap and effective weapons parts quickly. But this is the first time somebody has managed to turn out weapons parts privately. HaveBlue’s fairly experienced: he recently made most of a .22 pistol using 3D printing.
It’s worth noting you can’t download a gun’s schematics and hit “print.” There are still parts you’ll need, such as the barrel with proper rifling. What this does do is drive down the cost substantially and make it possible for weapons enthusiasts to experiment with their own designs.
3D printers are only going to become more common: you can already build them yourself out of widely available materials. All that said, when it really comes down to it, if I’m going to build my own weapon, I’m going to build the crossbow revolver.
A Working Assault Rifle Made With a 3D Printer [Popular Science]