Gonna go ahead and refer you to the chart. Note that gun violence is actually going down as we remove restrictive gun control legislation. Many states are now shall issue states and there are no more no issue states. Also note each "peak" corresponds with gun control legislation being passed.

Nope. You *[b][i]Cannot[/i][/b]* 3D print a whole gun. Or even most of one. All of the internals would still have to be made out of metal. upper receiver, Bolt, Firing pin, barrel. Would all need to be metal. If you made them via 3D printer they would likely not even fire a bullet. In the event it did fire the round, it would explode instantly. likely causing decent injury to the shooter. and a couple people around him If they were standing close. Doing that wouldn't even be effective as a blast weapon.