To have a gun you need a reason, self defence for some EXTREMELY stupid reason is not one of them, UNLESS you're an Australian Police Chief.
I have a handgun under target pistol licence which limits me to barrel lengths from 120mm for semi auto to 100mm for a revolver. No caliber over .38 unless you pay money to get accreditation for metallic silhouette or Cowboy Action which you also need a rifle licence to participate in (unfortunately pistol licence doesn't count for rifle). Even if you did have the accreditation you can't have a pistol over .45 cal. All must have a mag cap of 10 rounds.
If you have a collectors licence you can have the guns with shorter barrels and large mag caps, but you're not permitted to shoot them or you'll go to jail.
Semi-auto collectors rifles must be rendered permanently inoperable.
No semi-auto rifles, no pump action shotguns (rifles permitted) unless your jobs requires it. You could get it if you had a lot of land and participate in olympic shooting.
The way you can get rifles is to say you're a hunter or target shooter there are more reasons, but I've forgotten since I can't afford a rifle licence as well.
Security guards can carry guns, but that's only to protect themselves and money which is stupid BS considering they never use them.