A large number of gun owners, those programmed by years of regulation and rule would turn their guns in.
Don’t believe it, its happened before.

A great Grandfather turned in a Colt SAA to the Chicago Police when they implemented the ban.
(Didn’t say he was the brightest)
But he and many others did just that.

Look at those who turn in guns for gift cards.

It won’t be a roundup, but a slow and methodical end to private possession.