I think that once 3D printer tech matures and brings some top-level manufacturing capabilities to small dives on a budget (maybe providing tech optimization tools to squeeze higher quality out of the prints.
Guns made from 3D printers are notoriously poor quality, b/c the ABS/PLA material used to make the prints can't withstand even 3 bullets firing w/o melting the barrel beyond use, so those worrying about would-be murderers manufacturing uzis and colts in their bedrooms don't need to worry much...their guns are going to suck hard.
I'm really intrigued w/ 3D printers for a different reason tho, so far as making scale models and controllers. Time to re-learn AutoCAD...
At least, I hope once 3D printer tech matures and brings some top-level manufacturing capabilities to small devs on a budget (maybe providing tech optimization tools to squeeze higher quality out of the prints, on behalf of the user's knowledge to do so), gun control policies won't try to outlaw them or make people who have them pay an extra tax....maybe a license wouldn't be a bad idea tho.
You do not need a plastic gun to fire a full clip. You just need an angry kid with the time and resources to make a gun and use it in a crime and the shitstorm about 3D printing will begin and never end.