Re: No, it's not settled
"It's why, for example, the UK has historically had very low gun crime; we used to punish it harshly."
Punishment to deter crime doesn't work; it has been used for centuries but still hasn't stopped crime. But that's an entirely different kettle of fish.
I'm strongly inclined to believe that the UK's relatively low gun-crime rate has been more due to both cultural differences (the majority of people don't want to live in a society where personal ownership of guns is seen as a necessity to personal safety) and the relatively low numbers of guns in circulation.