3D printed guns
Never understood the point.
Well, maybe the philosophical one regarding "when is a gun a gun and not a collection of parts" but if you're going down that road you might as well build a lower receiver by hand or on a lathe.
It's perfectly possible to make a better "gun" from your local DIY store. Even the crudest pipe rifle is probably safer and more effective than a printed gun.
Or you could just take the money you spent on a 3D printer and buy an actual gun. An AR15 is what $500 or so?