Some have said that there has never been any confiscation of guns in the US, but I remember differently.
In Ohio, I believe, many years ago, a city passed a law forbidding the sale of “Saturday night specials”.
An injunction was placed against the city and the guns continued to be sold AND REGISTERED.
The courts sided with the city and upheld the law, the the city sent out notices to those who had bought guns, after the first ban date, to TURN THEM IN.
Both New York City and Washington DC both passed registration laws, on Nields's template, while swearing up and down that they were NOT going to confiscate any weapons, they needed the information for other reasons, that the opponents of registration were being unreasonable and frankly hysterical.
They waited about two years and then sent police door-to-door. One knock, no notice, on-demand surrender your weapon now or go to jail now.
That's how they did it.