So, I had a quick search online and found the following:
State laws govern the possession and use of firearms in Australia. These laws were largely aligned under the 1996 National Agreement on Firearms. Anyone wishing to possess or use a firearm must have a Firearms Licence and, with some exceptions, be over the age of 18. Owners must have secure storage for their firearms.
Before someone can buy a firearm, he or she must obtain a Permit To Acquire. The first permit has a mandatory 28 day delay before it is first issued. In some states (e.g. Queensland, Victoria, and New South Wales), this is waived for second and subsequent firearms of the same class. For each firearm a "Genuine Reason" must be given, relating to pest control, hunting, target shooting, or collecting. Self-defense is not accepted as a reason for issuing a licence, though it may be legal under certain circumstances to use a legally-held firearm for self-defence. [4]
Each firearm in Australia must be registered to the owner by serial number. Some states allow an owner to store or borrow another person's registered firearm of the same category.
[edit] Firearms categories
Firearms in Australia are grouped into Categories with different levels of control. The categories are:
Category A: rimfire rifle (not semi-automatic), shotguns (not pump-action or semi-automatic), air rifles, and paintball markers.
Category B: centrefire rifles (not semi-automatic), muzzleloading firearms made after 1 January 1901.
Category C: semi-automatic rimfire rifles holding 10 or fewer rounds and pump-action or semi-automatic shotguns holding 5 or fewer rounds. (Restricted: only primary producers, occupational shooters, collectors and some clay target shooters can own functional Category C firearms)
Category D: semi-automatic centrefire rifles, pump-action/semi-automatic shotguns holding more than 5 rounds (functional Category D firearms are restricted to occupational shooters; collectors may own deactivated Category D firearms).[2]
Category H: handguns including air pistols, deactivated handguns and guns less than 65 cm long. Target shooters are limited to handguns of .38 calibre or less.
(Participants in "approved" competitions may acquire handguns up to .45", currently Single Action Shooting and Metallic Silhouette. IPSC shooting is not "approved" for the larger calibres, for unstated reasons. Category H barrels must be at least 100 mm (3.94") long for revolvers, and 120 mm (4.72") for semi-automatic pistols, and magazines are restricted to 10 rounds. Handgun collectors are exempt from the laws stated above.)
Category R/E: restricted weapons: machine guns, rocket launchers, assault rifles, flame-throwers, anti-tank guns, Howitzers, artillery, .50-calibre BMG weapons, etc. (Collectors in some states only, weapons must be comprehensively deactivated. Deactivated firearms are still subject to the same storage and licensing requirements as 'live' firearms in many states.)
Antique firearms can in some states be legally bought without licences. In other states they are subject to the same requirements as modern firearms.
All single-shot muzzleloading firearms manufactured before 1 January 1901 are considered antique firearms. Four states require licences for antique percussion revolvers and cartridge repeating firearms but in Queensland and Victoria a person may possess such a firearm without a license, so long as the firearm is registered.
Australia also has tight restrictions on air pistols, airsoft guns, and replica firearms. Suppressors (or 'silencers') are extremely restricted and generally not available to most shooters.[3]
http://en.wikipedia.org/wiki/Gun_politics_in_Australia
Now, I will admit I know nothing about guns and half of what was written there makes no sense to me at all..but how do these laws differ from America's?