Those are dealer sales only via FFL. No records of sale or transfer is
required by most states, as far as I know. MA seems to be one of the
few that maintains a record of private transfers, but it's almost
voluntary. You are supposed to report it on-line but there's no way of
determining if everyone does. However, if ever used in a crime and
found, it would be traced back to the original purchaser (via FFL)
unless transfers *have* been reported as required. That is the
motivation to comply.
The good guys will comply with whatever laws exist.
If only they could find a way to track guns in the possession of the bad
guys who really don't want you to know?