Here in Oz we had the Port Arthur massacre. Straight after that the government banned assault weapons.
They did a buyback scheme which did bring in a lot of guns, but I know a lot of guys that have hidden weapons away. Some have even buried them. There are a lot of guns here, but we don't have the crime like they do in the US, and also not as many people.
The PM here had to wear a bulletproof vest for a while after bring out about the ban.
If the US tried to do something like that the president would be dead in a week.