Obama has said outright that he would ban all semiautomatics, and he's foolish and naive enough to do it.
Hillary may be an evil ice queen, but she's also shrewd, and knows it'd be political suicide to do so in the long term. She'd get to it eventually, and probably push for AWB II, but Obama is naive and inexperienced enough to actually call for confiscation of all semiautomatic weapons, rifles and handguns, even if it resulted in armed revolt.
He doesn't know better.