Our gun laws worked exactly as advertised, after a string of US style mass shootings in the late 80's / early 90's the laws banning semi-automatics were introduced, the catalyst being the Port Arthur massacre that claimed 30+ lives. Since the laws were introduced 20+yrs ago there has not been another mass shooting in this country. Since mass shooting had been rare the effect on the murder rate was insignificant. Gun deaths are still around 200 souls per year, there are towns in the US that have a higher rate than our entire country, this fact has nothing to do with the law and everything to do with the culture inherited from our colonial past.
This may be extremely difficult for an American to understand but "self-defence" is not a valid reason for granting a gun license in this country. Nobody living here needs a semi-auto rifle/shotgun, and very few of us would want one anyway. However before you start raving how stupid we Aussie's are, what other country can you name where the leader can go for a regular morning jog in the street without a small army of heavily armed body guards following him around?