Any reason other then self defence.Understood, excuse my ignorance. What exactly is the OP getting at here? Does he mean the right to bear arms without any form of training or license therefore the right to carry a handgun like what exactly, a Swiss knife? No.
Also I believe currently you need solid reason to own a gun in Australia, for example:
security guard
private investigator
farmer
collector
hunter?
In reality all you need is a class b safe, ammo safe, a local club, bg check nd some training.
This is why most bogans dont have guns, because they need permission to install a safe.