So my solution is to treat guns like cars.
Categorize weapons, eliminate the gray areas like AR pistols. Different age requirements for different weapon categories. Hunting guns are cool at 18. Semi auto pistols at 21. Semi auto long guns, 25.
License to operate based on categorization. Standard hunting weapons like pump shotguns and bolt rifles? Standard license. Semi auto? Class B license, little more work to do, etc , etc. Require refresher training/testing at certain intervals
Insurance requirement for weapons. Categorization drives premiums. Risk factors also drive premiums. You want an AR-15, live in the burbs, and have kids in the house? Man that’s like making your 16 year old the full time driver of a red Ferrari. You can do it, but it’s going to hurt. Standard hunting guns, no kids, verified gun safe? Pocket change. Discounts based on safety gear and number of years of accident free ownership. Policy does not pay out if your gun is used in a crime. This goes hand in hand with some stiffer civil penalties if your gun is used in a crime.
Registration for weapons. Closes the loop on existing weapons. Enact a sliding scale of wait period based on weapon category, owner age, other factors. Require proof of insurance at pick up.
Will this stop someone from illegally owning a gun, that isn’t registered, that isn’t insured? No, just like all our car laws don’t stop someone from driving a car that isn’t registered or without required insurance. It gives gun owners a financial incentive to do basic things like secure their weapons so a kid can’t use them. It gives the police and prosecutors more things to throw at irresponsible gun owners. Trying to take guns away in this country is a pipe dream, so build a structure around them to increase safety. That’s about the best we can hope for.