One Sensible Piece of the Guns and Schools Issue

Are any of the guns you're contemplating capable of 18 rounds in under 4 seconds (average seasoned user, not Miculek, the pro hired gun, endorsed by Smith & Wesson)? 

if so, then purchaser should have to also purchase "good behavior" bond of $2,500, at time of purchase. Refundable after one year, with interest. This prevents the buildup of arsenals, and greatly reduces straw man black market supplies of such weapons. 

If you can't show that you've sold it legally, or you've reported it stolen, bye bye $2,500. 

If the gun is found anywhere, thereafter, it will be destroyed, thus making ownership via black market weapon a really stupid thing to do. 

Existing guns, not in the database, are assumed to be in the hands of the correct owner.  The owner's detailed  profile will then be added and and noted in the database, which is of course accessible by LE, nationwide.  If you don't want this to happen, don't do stupid things with your weapons in front of law enforcement.

Functionality counts, not name brand, or rifle /pistol designation.

An 18 year old single male with $3,000 is likely to find better things to do with that kind of money.

A gun that has a $2,500 bond attached to it is way more likely to be well locked up, and dog(s) and sensor lights installed, the sane way to deal with home invaders.