@gcblasing Also #AssaultWeapons per very definition are banned since the closure of the Machine Gun Registry...
https://en.wikipedia.org/wiki/Firearm_Owners_Protection_Act#Ban_on_new_automatic_firearms

In short, #AssaultRifles, #SubmachineGuns, #MachinePistols and #DesctructiveDevices can't be sold to civilians, and the few in circulation are so prohibitively expensive, no #MassShooter I've heard of was able to acquire one legally or even illegally.