"The Australian gun buybacks of 1996 and 2003 were compulsory compensated surrenders of newly-illegal firearms.
The 1996 Buyback took 600,000 newly illegal sporting firearms, including all semi-automatic rifles including .22 rimfires, semi-automatic shotguns and pump-action shotguns. The publicity and use of the misleading framing ‘automatic and semi-automatic’ term gave the impression that the main target was what are called in the US media ‘assault weapons’, but almost all were sporting rimfires and shotguns. Because the Australian Constitution prevents the taking of property without just compensation the Federal Government decided to put a 1% levy on income tax for one year to finance the compensation. The buyback was predicted to cost A$500 million and had wide community support.
The 2003 handgun buyback compensated the confiscation of about 50,000 newly illegal pistols, the majority being target arms of greater than 9mm calibre (generally used for IPSC competition), or smaller handguns with barrels less than 4" such as pocket pistols, which were mostly licensed for target use as since 1996 licenses cannot be issued for self-defense in Australia. Even anti-gun activists criticised this exercise as pointless because almost all of the confiscated firearms were immediately and legally replaced with others that met the new rules."
Source: Wikipedia.
Following the 1996 ban, the number of homicides in Australia decreased from 104 (year of ban) to 47 in 2001 (-54.81%) to 30 in 2011 (-71.15%). They still have 3,000,000 firearms. The ratio is 1 death every 100,000 weapons.
By comparison, the number of deaths by firearm in the US in 2011 was 9,146. The ratio is 1 death every 29,521 weapons.
As you can see, the difference exist. And it’s also non-linear, but a 3-and-1/2-fold increase.
Source: Australian Institute of Criminology (table 1) and The Guardian.