Firearms data bases are a simple fact of life today. Anytime the powers that be want a list, they can just data mine for folks who have purchased ammo or gun accessories with a credit card in the past ten years. Bingo. You have bought some 5.56 ammo and mags? It’s not a secret, not to LE.
That and a compliant citizenry is all they need. Just look to California, Chicago, DC, NY.