They made up the term assault weapon so they could ban weapons that look like assault rifles but really aren't. To be an assault rifle it needs to have select fire but that is banned already or at least requires a very expensive license and tax. If the assault weapon ban had still been in place the difference would have been his gun didn't have a pistol grip but instead had a thumb hole, unless he chose to buy a new one, and he would have had to have bought one of the very many used high capacity magazines out there instead of buying a new drum that jammed on him. Even if he had bought the required ten round clip with very little practice he could have learned to drop one and load and he might have actually been more deadly since they jam less. Not sure how that would have really changed things. Banning things because we give them scary names or they look scary really doesn't make much sense. Charles Whitman killed 13 at UT and all his weapons were standard hunting weapons.