The measure would place exemptions on recreational weapons used for hunting as well as ammunition. The law would not retroactively apply to tens of millions of AR-15s that are estimated to be circulating around the United States. In an attempt to define what would be taxed, the bill says it would apply to “semiautomatic assault weapon[s],” which are semiautomatic rifles that have the capacity to use a magazine that isn’t a fixed magazine, a pistol grip, a forward grip, and a folding, telescoping, or detachable stock. Other items that fall under that definition include a semiautomatic rifle with a barrel...