If they come to take your registered guns they will ransack all your property with metal detectors and ammo sniffers to find any other guns you are expected to have. Keep unregistered guns and ammo off property. And don’t think there is not gun registration. Every receipt you receive in a gun store represents a de facto registration. Every background check is a registration of your probably ownership of a gun. ANd no records are ever destroyed. Ever.
One of the largest gun registration systems in the world is the hunting license.
Get a large game license, they know you have a rifle.
Get an bird license, they know you have a shotgun.
The hunting license means you have a gun.. They know that much.
14.8M according to this 2015 report ( http://wsfrprograms.fws.gov/Subpages/LicenseInfo/HuntingLicCertHistory20042015.pdf ) And they know the names and addresses.
21.8 million Americans hunted at least once over the past five years ( https://www.nssf.org/PDF/HuntingLicTrends-NatlRpt.pdf ) And they know the names and addresses.
Etc.