There is no such thing as Federal gun "Registration"
because of false script writing from Hollyweird, 70% of the US population believes that there is a Federal Data base and all guns everywhere are "Registered" to a specific owner. And all you have to do it look up the serial number.
That is 100% false. There are laws safeguarding gun owners AGAINST the feds keeping a list on who owns what gun. Besides, private sales of guns in state face to face require NO bill of sale or any record of any sort. This is all part of our Second Amendment rights.
There ARE a few states that have blatantly unconstitutional laws about hand gun registration. ONLY law abiding citizens abide by these laws and zero criminals abide by those Draconian laws. NY, HI, and Washington DC have hand gun registration. Kalifornia will soon have "scary looking rifle" registration, but no hand gun registration.
So, when a gun is recovered at a crime scene usually the MOST that a serial number will tell is if a gun has been reported stolen by the owner. It is a Hollyweird TROPE to instantly track down who the gun is "registered" to. I repeat, there is NO SUCH thing as Federal gun registration.
Even if you have a carry permit, no guns that you own or do not own are on file. In most states you dont even have to OWN a gun to obtain a permit to carry. Like here in Florida.
We LEGAL gun owners all go through a national background check for ANY gun we buy that is not a private face to face sale. Those types of sales are pretty rare. 90-95% of the time guns are purchased through a dealer. Even guns bought from a dealer at a GUN SHOW...we must go through the exact same background check.
We get a little upset when the media and Hollyweird distorts and manipulates how things really are. I would bet tha close to 100% of NON gun owners have not even a tiny clue as to how gun purchases really work. And what the various gun laws are from State to state. They should all be 100% the same under the US constitution. Unfortunately the laws vary greatly from state to state.