For all the anguish and outcry in the days after a community college dropout named Jared Loughner allegedly sprayed a Tucson crowd with 33 bullets from a semiautomatic pistol, one response was notably absent: any sense that America’s latest shooting spree, which killed six people and wounded 14, including Representative Gabrielle Giffords, would bring new restrictions on the right to own or carry large-capacity, rapid-fire weapons.