Want to cut down most of your gun violence? It's obvious where the vast majority of US gun violence comes from. It's fairly easy. Just make up a set of rules that prevents the following sorts of people from having a gun license.
1. No virgins.
2. No one belonging to a loser/loner/antisocial movement of some sort (MRA/incel, 8chan, etc..).
3. No one who without an active in-person (not online/chat) social life.
It won't prevent all gun violence, but it will probably cut down annual mass shootings in the US from 400+ to under 5 per year. Additionally, it will likely drop the suicide rate significantly since the people who shoot themselves will have to try other less-effective means.
I describe myself as a little dose of toxic masculinity.