The case of Australia:
Our 1996 reforms were precipitated by the Port Arthur massacre, the 13th mass shooting in 15 years in which five or more victims died in places like Hoddle and Queen Streets in Melbourne and Strathfield Plaza.
The central provisions of the reforms were the ban on semi-automatic rifles and pump action shotguns, accompanied by gun amnesties and two national buybacks, which together saw some 820,000 guns destroyed. Because of their rapid firepower, semi-automatics are the guns of choice for those intent on killing many people quickly. John Howard introduced the reforms to prevent US-style mass killings....
In the 12 years since the law reforms, there have been no mass shootings.