You can take away all of the types of guns and clips all you want. You can arm someone at the door or in the classroom all you want. It still does not eliminate the element of surprise. Take the guy from the movie theatre at the Batman opening. He walked in from an exit and people thought he was part of the show. If he would have been armed with say only a standard handgun and a shotgun, and the entire crowd was armed, he still would have killed some people by the element of surprise. Would he have killed or wounded more than he did? Most likely no. Would he have been shot dead instead of going to trial? Most likely, yes. But it would have been no less tragic as some people would have lost their lives even if they were armed.