Background checks for private transfers is defacto registration. The gov will know who owns every transferred firearm and the owner will be accountable for it when they decide to confiscate them (claiming it was lost in a boating accident won’t help you).
Well.....the 4473 form registers the point of initial sale, that’s all. A citizen does not have to file a 4473 when selling a gun. Hillary wants to change all that but right now the law allows unregulated private sales.
If BATFE knocks on your door with a stack of 4473s you can legally say “I sold all those guns”. No record keeping necessary.
Might still get beaten up & imprisoned by jackbooted government thugs but the law is on your side.