Ghost gun printing is surging, but AI screening and microscopic toolmarks are helping slow untraceable firearm production.

And to be clear, like, the thing that we had to file was not the 3D-printed part. It was this kind of slightly crappy commercial part. I imagine that, for allegedly Mangione himself, ...

Some models — like the 3D-printed gun company Defense Distributed’s “Liberator” — can be made almost entirely on a 3D printer. Others require many additional parts, which are often metal.

Part of the gun that the police believe was used to kill the C.E.O. of UnitedHealthcare was made by a 3D printer using a popular design found online.