There is really no way you can draw those sorts of comparisons between the USA and Australia with regard to gun laws
FACT -- All that John Howard did was remove guns from the normal population.
His laws did not have any effect on the criminal / crazy group, who as we have seen have no problem with going to their local outlet and getting what they want
The character of the Australian public has started to change with the importation of people to whom crime, killing, shooting and similar has been a normal way of life for them them, prior to that Australians were more into a good old punch up to solve problems rather than going to a gun show to buy combat weapons
Of course we need laws to control gun use and their purchase in the same way we have road laws, as well as all the other laws, rules and social matters that combine to give us a safe civilized society.
The USA to the minds of most Australians have minimal laws regarding guns
Also there is ammunition control which appears to be a factor lost in the discussion
