Steps to locate your guns:
Contact manufacturer and force them to give up lists on who they shipped guns to. (This info is required by law)
Contact retailer and force them to give up lists on who they sold guns to.
Contact owner (you) and threaten them until they comply. This is what other dictators have used.
The loophole for owners is that they can get rid of their property as they see fit. You can put a blowtorch to all your weapons (hypothetically) and no one can say anything about it. “Sorry Mr Confiscator, I destroyed/threw away that weapon two years ago”
I think that all that is needed is if you want to buy a weapon that you should be required to show proof that you attended a firearms safety course.
Every FFL in the country has to maintain all sales records. My local gun shop has 20 years worth of 4473s. It would only require that ATF request every last one of them for registration to occur.
I’ve sold nearly all of mine, well, except the few I’ve purchased recently with the funds from the sales of previous ‘tools’. The gunshow last weekend was astonishly busy ... and ARs were nearly tripled in price. Ammo was leaving on hand carts!