On 10 May 1996, 12 days after 35 people were shot dead and 18 seriously wounded by a gunman at Port Arthur, Tasmania, Australia’s state and federal governments agreed to enact uniform gun control laws. Between June 1996 and August 1998, the new restrictions were progressively implemented in all six states and two territories. As the Port Arthur gunman and several other mass killers had used semi-automatic weapons, the new gun laws banned rapid-fire long guns, specifically to reduce their availability for mass shootings. Under the 1996–7 Australian Firearms Buyback, 643 726 newly prohibited semi-automatic and pump-action rifles and shotguns were purchased by the federal government from their civilian owners at market value, funded by a levy on income tax.1 Tens of thousands of gun owners also voluntarily surrendered additional, non-prohibited firearms without compensation.2 In total, more than 700 000 guns were removed and destroyed from an adult population of about 12 million. Australia’s revised gun laws also require that all firearms be individually registered to their licensed owners, that private firearm sales be prohibited and that each gun transfer through a licensed arms dealer be approved only after the police are satisfied of a genuine reason for ownership. In this context, possession of firearms for self-defence in Australia is specifically prohibited and few civilians are licensed to possess handguns. A detailed summary of the reforms can be found in Ozanne-Smith et al. (https://injuryprevention.bmj.com/content/10/5/280?ijkey=72db6ac9774068d86616fe74a8c23aeff51e7a5e&keytype2=tf_ipsecsha

Results: In the 18 years before the gun law reforms, there were 13 mass shootings in Australia, and none in the 10.5 years afterwards. Declines in firearm-related deaths before the law reforms accelerated after the reforms for total firearm deaths (p = 0.04), firearm suicides (p = 0.007) and firearm homicides (p = 0.15), but not for the smallest category of unintentional firearm deaths, which increased. No evidence of substitution effect for suicides or homicides was observed. The rates per 100 000 of total firearm deaths, firearm homicides and firearm suicides all at least doubled their existing rates of decline after the revised gun laws.

Conclusions: Australia’s 1996 gun law reforms were followed by more than a decade free of fatal mass shootings, and accelerated declines in firearm deaths, particularly suicides. Total homicide rates followed the same pattern. Removing large numbers of rapid-firing firearms from civilians may be an effective way of reducing mass shootings, firearm homicides and firearm suicides.

More details on Australia's approach and it's impact on the country can be found here: https://injuryprevention.bmj.com/content/12/6/365