Maybe we should make those almost impossible to own? We could drive up the price to $20K maybe.
Weren’t fully automatic weapons placed under extremely severe limitations back in the days of FDR? The National Firearms Act of 1934, and later amendements to that law, made the acquisition of ANY fully automatic weapon by a civilian a long, difficult, and expensive undertaking. It is not likely that the typical mass shooter would qualify or have the perseverance to try to obtain such a firearm.
Might steal one, if he knew where a collector might be keeping one, but the degree of security surrounding such an item would give even a CIA operative considerable pause. Not that the deranged prospective shooter would likely ever have the discipline to become a CIA operative, or even get in the front door.
But hey, automatic rifles make a great prop in action movies.