But there are two things that are needed for a gun to work: the gun and the ammunition. Limiting guns may be hopeless. So why don’t we focus on the bullets?
People have made their own guns for a long time. A ZIP gun, a crude device used in prisons and by street gangs, can be cobbled together with only a little more effort than Defense Distributed’s plastic offering. A gun can be made from any number of common household objects. But making bullets is much, much trickier. A bullet needs much more specific consideration of materials and weight and requires something that is much harder to come by: a propellant. You can make your own gunpowder, of course, but refining the process to create effective munitions is as tricky as building a simple bomb. Doable, but dangerous.