In Australia 12 years can join gun clubs and own weapons when of age, there are classes of gun licence, if someone wants to work as a feral pig shooter they can get a semi automatic weapon.

The significant factors in Australia are that guns are regulated uniformly across all states, all sales either through dealers or privately are tracked, gun licenses can be revoked for improper handling, storage, domestic violence convictions, etc, and can be suspended for a period while allegations of particular nature are sorted out.

So, guns are treated as seriously as explosives, poisons, other dangerous goods, and they are efficiently tracked and databased (unlike the US with inconsistent regulation and no central electronic databses, etc).