Don't allow criminals to own guns, and they increasingly drop out of circulation. Don't issue them unless there is good reason for them to have it and they have a clean record

Self defence here in Australia isn't a valid reason to own a gun

This also allows the people who sold the guns to be arrested too.

The fact is, if a criminal has a gun, you're not using a gun to defend yourself. They have more experience and are more prepared.

Here in Australia, I was actually in a near school shooting which was stopped because it was only a hand gun and because someone with martial arts experience took him down

Your other problem is that you guys let kids use guns, so that turn it into paet of their identity