It is not what we do with what we create, but what others do.
They have now free templates online to make and load 3d printable runs. The hobbyists who make them are having fun, making strange and ornate weapons and meeting to shoot on ranges. But the guns are obviously untraceable and can kill.
So now they will be used by criminals and of no use as ways of finding them so no gun user needs to be afraid of throwing their guns away after a robbery. Or of being found with it because it could be one of thousands exactly the same.
Good going US.