I don’t even own a gun, so maybe somebody with more experience can correct me, but I do believe that many states, if not all, require a background check and waiting period. I assume there are certain crimes that remove your right to own a firearm. There are (or were) loopholes for purchasing guns at gun shows where a background check and waiting period are infeasible.
As for other weapons, there aren’t such provisions, but it may depend on the weapon. A bow and arrow, hunting knife or machete can be purchased at any wall-Mart. A grenade? I’m not sure.
That was sort of my point. I’m going to go out on a limb and say without any research that bears kill more people every year than 3D printers.