This, and more importantly, most of these small towns where gun ownership per capita is quite a bit higher than average also depend on the sheriff for SWAT type actions. That means his team will be handling everything in the county and cities, so you'd be looking at 10-12 SWAT officers to go door to door on 12,500 households totaling 33,000 people. Even if they split into three four man squads and did a search every 30 minutes, 24x7, it would take most of a year to get it done. During that time, I would bet there would be a lot of people setting up some very effective resistance. All of this assumes the (elected, and by people who like the 2nd Amendment) sheriff is even willing to help with a confiscation.
And this also assumes that there are no injunctions issued by courts to cease and desist the searches, or a suspension of 4A to legally permit a house-by-house search, which would get a lot of libs fired up.
All of this is why I truly believe that confiscation searches on this scale won't happen. Too many problems across the board. And, if they tried, can't you imagine a lot of unregistered firearms would disappear before they got to the owner's home? Hell, guns aren't like drugs or explosives. Never heard of a gun sniffing dog. So they would have to rip out the walls, tear up the floors, etc to check everywhere possible. I would hope that level of searching would get everyone fired up, especially a bunch of lawyers and judges. Yep, gotta set asiee the Constitution and eliminate judicial oversight...
Absent a declaration of the First American Empire, not bloody likely.