Passed by Congress on Sept. 13, 1994, and signed by Bill Clinton later that day, the Federal Assault Weapons Ban prohibited the manufacturing of 18 specific models of semiautomatic weapons, along with the manufacturing of high-capacity ammunition magazines that could carry more than 10 rounds.anza's primary weapon, the Bushmaster .223 rifle, is a type of AR-15 semiautomatic rifle, certain models of which were prohibited from being sold under the ban, but the Bushmaster model used by Lanza was not on that list.