Myth: Gun control in Australia reduced gun homicides and suicides tremendously.
-Australian gun control and Mass Shootings
In 1996, the Australian government instituted strict gun control measures which made it almost impossible for a civilian to own a semi-automatic rifle or shotgun after a mass shooting which left 35 people dead (the even restricted access to airsoft guns). Since then, Australia hasn't witnessed a mass shooting, leading many gun control advocates crediting the 1996 gun control legislation as the cause of the lack of mass shootings. Are they right? No.
A 2011 study published by the Justice Policy Journal examined the incidence of mass shootings in Australia and New Zealand over a 30 year time period. The results don't provide any evidence in favor of the belief that banning guns reduces mass shootings. According to the authors:
"[The results do]not find support for the hypothesis that Australia’s prohibition of certain types of firearms has prevented mass shootings, with New Zealand not experiencing a mass shooting since 1997 despite the availability in that country of firearms banned in Australia." 
- Gun control and firearm homicide and suicide
After the 1996 gun control legislation, firearm homicide declined, leading gun control advocates to credit gun control as the cause of this decline. However, firearm homicides were already declining before the gun control legislation passed. A study published by the University of Melbourne studied the effects of the 1996 gun control legislation on firearms homicide and suicide. The authors report:
"The results of these tests suggest that the NFA [the gun control legislation] did not have any large effects on reducing firearm homicide or suicide rates." 
Additionally, a study published in the British Journal of Criminology found that there was no evidence that the NFA [National Firearms Agreement] had any impact on reducing firearm homicide . They did find that it may have helped reduce firearm suicide, but they that societal factors were already reducing suicide rates.
Lastly, a 2009 study the Australian Institute for Suicide research studied how the NFA effected suicide rates and found the following:
"The implemented restrictions may not be responsible for the observed reductions in firearms suicide. Data suggest that a change in social and cultural attitudes could have contributed to the shift in method preference". 
So now you have the facts. Do with them as you will.