This is the way I as I know it, correct me if I'm wrong...

Category A Licence:
Firearms allowd - Bolt, pump or lever action rimfire rifles
Requirements - Own or have access to a farm to hunt on

Category B Licence:
Firearms allowd - Bolt, pump or lever action centrefire rifles up to .77cal, break action or lever action (up to 8 bore) shotguns.
Requirement - Similar to above but these are slightly harder to get, still not difficult though.

Category C Licence:
Firearms allowd - Semi auto centrefire or rimfire rifles, pump action & Semi auto shotguns.
Requirements (not as sure on this one)- Must be primary producer (farmer). Not sure of the exact reqirement for this licence. Very hard to get.

Category H Licence:
Firearms allowd - Auto-loading pistols with a minimum barrel length of 120mm & revolvers with a minimum barrel length of 100mm. Maximum calibre of .38/9mm unless you are registered as a shooter of an event that requires larger, in this case you may own anything up to and including .45cal. It must also have a capacity of 10 rounds or less. Gun must not be used outside the target range on which it was registered for use.

There are also special licences that vetrinarians and primary producers may obtain for putting animals down. Any gun must be in a locked gun safe and the ammunition must be stored at least 5m away in a separate safe. If you wish to own anything bigger than .77 cal you must obtain a cannon licence...

M82A1

PS
Feel free to correct me on any mistakes and add in any other parts that I have forgotten...