1986 Bush 1
George Bush Senior signed the law preventing further import of look-a-like semi auto "Assault type weapons" including high capacity and revolver type shotguns.
The ban also extended to semi auto surplus rifles, this is why you don't see any SVT-40 and SVT-38 rifles, Dragunovs and Medveds, FN49, Hakims, Rasheeds, etc.
The guns are out there, thousands of them, all surplus and waiting for buyers.
Clinton AWB expanded on this law by preventing domestic firearms from having features such as flash hiders, bayonet lugs, and high capacity magazines from being sold to general public though items already on the market could continue to be sold, mainly because the goverment was well aware of the costs involved in trying to seize the stuff and the costs involved in arresting and prosecuting the possessors.
Blame both the Republicans AND the Democrats, remember both parties are only looking out for your best interests!