[Blood of Tyrants]

"If you were just to do new firearms, that basically means that there would be 200 million firearms that would not be traceable in this system,"

No problem (for the gun grabbers). The simply pass a law forcing all FFL holders to turn over their Form 4473's and then a law to attempt to force all gunowners to bring their guns in for "fingerprinting". While you are at it, you can leave a DNA sample for the police.

[Mr. Lucky]

...and of course, anyone bent upon mass murder would be decent enough not to modify his weapon to alter the markings.