The gov doesn't have to go door-to-door to get guns.
They just make a few high-profile busts on TV, use the media to demonize the few patriots who actually have the cajones to go down fighting, and the majority of gun owners will pee themselves racing to comply.
Those left will have to hide their guns so deep as to make them essentially useless.
Just ask the IRS how easy it is to intimidate the masses into compliance with unpopular legislation.
We need to stop asking "who will pay for healthcare" and start asking "why does it cost so much?"