The thing I don't get is how a plastic gun suddenly becomes a problem if it's 3D printed.<p>You can construct (a very crude) gun barrel for .22LR out of 3/4" plastic bar using nothing more than a 1/4" drill bit. You need a mechanism to fire the round, but since you just need to crush the primer, it doesn't have to be anything fancy. Of course you have no rifling and a poor seal so the bullet tumbles and isn't effective more than 10-20 ft away, but it's deadly up close.<p>Since plastics became commonly available over 50 years ago, I don't understand why everyone is suddenly concerned about plastic guns from 3D printing. What is a criminal more likely to do, buy a 3D printing machine for several hundred dollars, learn how to use the software correctly and print a gun OR just buy some plastic and make one himself for $10 and a few hours of his time?