Right, and then everyone who (was) law abiding will say screw it and ignore every gun law instead of just that one in particular.
I can just imagine the proliferation of sawed off shotguns and home converted automatic weapons.
Speaking of which, how the hell will they stamp shotgun rounds??
Additionally, bullets entering a human body tend to fragment, so stamping a serial number on them would be useless most of the time. (except in the well-known case of the “magic bullet” that killed JFK. went through 2 bodies and a car seat.)