The Constitution gives us the right to bear arms, a gun, it doesn't mean ANY gun you want in any number you want, you can't have a Howitzer in your front yard. We had the federal assault weapons ban for 10 years. It's mind boggling how it hasn't been re-newed. The 2nd Amendment had nothing to do with owning guns for personal usage, that was a given that people back then needed guns, there weren't police departments and many people lived in rural settings, not to mention guns for hunting and sport. The 2nd Amendment's purpose was to protect the country from outside invaders, the British who were still in Canada, Indians and any foreign country that might invade our shores. The country was very poor at the time, it didn't have the money for a large standing army so the amendment made it legal for people/states to raise militias, men provided their own guns to join those militias, nobody else was going to pay for them. Why 'the right to bear arms' is the second part of the amendment. It's a complete myth that the 2nd Amendment's purpose was to give the people the ability to rebel against government tyranny but that myth is deeply embedded in American culture and the NRA plays on it to great effect.
The federal government could pass a law that made any gun illegal other than a non automatic rifle and handgun illegal to possess, more exotic guns would have to be stored at licensed regulated gun ranges/clubs.
It still wouldn't stop mass shootings but would cut down on the magnitude of carnage caused in Las Vegas, over 500 casualties, that is insane, those are numbers from a war battle. Stopping mass shootings is almost impossible in the US, the gun culture mentality isn't going to disappear with any laws for a long time and mentally unbalanced angry mothereffers aren't going to disappear.
As I've read on Twitter many times in the past 36 hours if the deaths of 30 plus little children in Sandy Hook didn't change anything nothing will. Mass shootings will continue.