Otherwise, you can buy pretty much anything non-automatic when you have a hunting or sports license. Neither is hard to obtain. The circulation is regulated but still quite simple. You can even sell a gun over post with cash on delivery.
Additionally, it was no secret who was a member of the home guard, so there were numerous cases of homes being burglarised for the AG3 stored there; the weapon was then used for further crimes, like bank robberies.
Now, weapons are stored at the home guard's places of assembly in case of mobilization.
Also, while I agree that it is no problem obtaining a hunting rifle or a shotgun (passing the test isn't THAT hard), a handgun is more complicated:
a) You need to have a clean criminal record, and be more than 21 years of age. Also, the local police must approve - say, it is (theoretically, at least) possible to be turned down even with no record if the local police do not think you are suited to own a weapon - say, if you regularly binge drink, are known locally as a trouble-maker or whatever.
b) You must have completed a safety course at an approved gun club. Typically 3-4 nights, intended to learn you how to handle the gun safely, know and follow shooting range regulations &c.
c) You must be an active member of an approved gun club, and must have been so for at least six months prior to applying for a purchase permit. Active basically means turning up at club events and shooting with one of the club's weapons until you have your own.
d) Yout licence may be revoked if you no longer have a need to own a weapon - say, if you stop showing up at club nights and let your membership lapse. Also, any problems with the law? Better take a good, hard look at that licence, because it will be revoked as soon as they get around to it.
e) You normally only get a permit for one weapon, unless you can lay credible claim to being a collector (in which case even more training and vetting is mandatory).
Being from #10 on that list, the type, quality and "outings" of guns matters a lot. In France, "owned guns" are either sport or hunting weapons, seeing one outside of hunting season basically does not happen and they're regulated:
* single-shot (per barrel) smooth bore long guns must be registered (for hunting or sports), buying requires showing an ID and either a hunting or a sports license (from an accredited gun club)
* air guns beyond 20j and various types of long runs replace the registering by a declaration (a more complex procedure)
* various more powerful and smaller weapons (including handguns) have to be authorised before they can be bought, for sports or defence (mostly professional). Amongst other concerns the would-be owner must have a clean criminal record, show a clean bill of health (physical & psych) under 1 month old and demonstrate ownership of a safe
* automatic, high-capacity (30 for long guns and 20 for handguns) and very-high caliber (>= 20mm) is forbidden
Guns must be disabled or under lock when not heading to, coming back from, or performing the activity they're used for.
I expect Norway, Finland, Canada or Germany are very similar: though specifics probably vary, weapons ownership is most likely regulated and generally restricted to hunting and sports (the licensed, olympics-able "Shooting Sports" kind, not the "I went at the range to play with a minigun" kind).