Just to clarify my earlier post:
I did not mean to imply that there was 'federal registration' per say, in which the fed gov't maintained records such as type of gun, ser. #'s etc. purchased at an FFL holder.
Sorry if there was a misunderstanding.
I was implying(and maintain) that there is federal registration(or call it what you will) 'by proxy' via the LGS/DEALER/FFL on guns purchased at theses places. As these entities are required by the Feds. to keep all this information available in the event they(the fed. gov't) see's the need to access it.
Also, the few states that do require registration of private sales are requiring it at the State,City, Co. level, not the Fed level.
Thank You JohnKSa for the legal explanations.