Honest question, and a hard one, short of banning guns and collecting them.....

[spanone]

29. austrailia 1996

In 1996, Australia passed the National Firearms Agreement after a mass shooting in Tasmania in April of that year. In that incident, a 28-year-old man, armed with a semi-automatic rifle, shot and killed 35 people, and injured 18 others, in what was known as the Port Arthur Massacre.

Under the 1996 law, Australia banned certain semi-automatic, self-loading rifles and shotguns, and imposed stricter licensing and registration requirements. It also instituted a mandatory buyback program for firearms banned by the 1996 law.

During the buyback program, Australians sold 640,000 prohibited firearms to the government, and voluntarily surrendered about 60,000 non-prohibited firearms. In all, more than 700,000 weapons were surrendered, according to a Library of Congress report on Australian gun policy. One study says that the program reduced the number of guns in private hands by 20 percent.

In 2002, Australia further tightened gun laws, restricting the caliber, barrel length and capacity for sport shooting handguns.

https://www.factcheck.org/2017/10/gun-control-australia-updated/