How about requiring a GPS locator chip embedded in all new weapons, somewhere in the metal so it cannot be removed without destroying the functionality of the gun, like the one we had put in our dog that has now found her twice? Doable, passes the cost along to the consumer, can be use to monitor weapons in general or track known weapons or do location sweeps of felons who are not allowed to possess weapons. Idk, just a though. There is lots of opportunity to abuse this of course, but it might be a starting point.
Could also make far stricter consequences for people who use guns in crime, such as mandatory prison sentences with no opportunity for parole for at least 15 years or similar (pretty sure there is already something similar in some states, tltg) Or let's make a registry like the sex offender registry for people who commit crimes using guns.
The toughest thing about policing all of this is the sheer number of weapons already out there, which makes it nearly impossible to establish any course of action like this, unless we want to use martial law to round them all up, then we are justifying using them the way the founding fathers thought we might need to in the first place.
For that to really mean something you need to change prison. No more cable tv, much more work. You are their as punishment and it should be harsh and difficult. It should make you never want to go back. Tent city AZ...