I honestly have no idea if this would work but what if instead of all this assault weapon, pistol, etc talk the US added a gun restriction that all civilian guns had to use something stupidly huge like a .50 BMG round? While that wouldn't prevent individual murders it would have a good chance of keeping people from firing a bunch of shots quickly, right? Building a semi-auto .50cal weapon with a bump stock or other such popular mass shooting tools seems like the recoil would take your arm off. Even if someone gets a M2 machine gun off the black market it's impractically huge and awkward for shootings in public places. You'd need to have a lot of strength to handle any weapon in this caliber.
Sure, it'd make building armored cars for celebrities very tough...
Sure, it'd make building armored cars for celebrities very tough...