The tyrant will have the organizational advantage. Once the guns have been registered, they will be able to deploy overwhelming force to reduce centers of resistance one-by-one. Resistance will be futile (to quote a fictional tyranny) for any armed individual opposed to the New Order.
This is the same method the Nazi’s used, of course. Registration first - but you may keep your guns. Confiscation second - now that we know what you have, you have no choice except to hand it over.
Pardon the correction, but this is one of the largest falsehoods spread across the internet. It was the Weimar regime in 1928 that registered, banned, then confiscated weapons. They did so in an effort to prevent the rise of the SA Voran "Brown Shirts" which were the National Socialist Party.
The 1928 law was subsequently extended in 1938 under the Third Reich (this action being the principal point in support of the contention that the Nazis were advocates of gun control). However, the Nazis were firmly in control of Germany at the time the Weapons Law of 1938 was created. Further, this law was not passed by a legislative body, but was promulgated under the dictatorial power granted Hitler in 1933.
What we can see here is a more sadistic version of what happened in 1928 and subsequently 1933. Sen. Feinstein and her ilk are hell-bent on subjugating the citizens of these United States and would be one of the first to grant dictatorial powers to her saviour BHO.