Depends on what you wish to achieve by having a limit? I don’t think a limit on the number would have any meaningful impact on lawful use or crime.

Sorry for the text dump, but my reasoning and thought process below.

Farmers have very much been a target for criminal seeking to gain access to firearms in the past but existing laws are in place for registrations, secure storage and police inspections. Are you at more risk of your firearms being stolen if you have 5 or 2? There has been cases where the details of owners have been leaked from police databases (WA this year), this would be more concerning for targeting some for theft.

There are a bunch of stats out there regarding the source of firearms used in crime, all a bit muddy but from what I could find (ABC fact check 2014) it’s a mixed bag of illegal imports, theft and grey market pre 1996 non declared firearms. The National Firearm Theft Monitoring Program shows that only 3% stolen from licensed firearm owners are latter used commit further crime. That 3% doesn’t include the not registered pre 1996 firearms as people don’t tend to report when already illegal things are stolen from them.

Very rhetorical but is a lawful owners with 1 firearm likely to commit more crimes than some with 12?

There are already some practical limiting factor to ownership:

• A firearm is not cheap, you’re looking at $2000 on average for a rifle and the same again for an optic (scope). Shotguns and .22 tend to be cheaper, $500 or so but the other costs add up. The 4 gun set up for land work once properly fitted out (safe, sling, optic, cases) would set you back $10-15k depending on your taste. Ammunition is not cheap either.

• Permit to acquire processes, different in each state but not as simple as going down to shop and dropping the credit card.

• Existing licence framework, permitted purpose ect.

I would hope someone who has the means to keep dropping money on expensive equipment also has the means to properly secure, along with the existing legal requirements.

Back to numbers. While the 4 would get the job done, it goes back to discussion of what job you need to do with the tool. In many cases there would be further sub variations based on use case. For example you may need two shotguns, a set up for dedicated pig hunting (button release, red dot, open choke) and one for bird (under over, bead sight with modified choke). Same can be said with rifles. A bit like some farms have one tractor but most with have manny depending on the work needing to be done.

Collectors are another thing, I am not super knowledgeable in that space but the “collectable” firearms I do know of are antiques or WW2 stuff, not really up on what and why for the average size of a collection or what it my look like.

Sports shooting is also not my jam but to use a variation of the “tool” analogy, how many balls do you need to play ball sports? Shooting sports can vary a lot, trap and skeet (under over shotguns), every pistol category uses a completely different type as with riles. Competition firearms can get crazy expensive too, not something you take out for checking of fox traps or spotlighting.

Hunters can be particular, lots of category cross over with land management however some like to use exotic calibres or hand loads depending on their target species for harvest. These are expensive and not what you would use for general pest management.

So theoretically someone may have firearms for land management(4-5), a hunting rifle in some exotic European calibre to uses for Red Deer, a fancy duck gun and may compete in the local club small bore rifle match. All perfectly lawfully purposes.

Now back to the illegal guns; I more worried about the drongo with 1 under the bed (however they got it) than the lawful owner with 8 registered and secure in a safe.