The firing pin indentation signature leads one then to speculate on the feds starting to "print" each and every firearm before it leaves the factory or dealer. Is that good or bad? This would certainly be a good instance. What would the downside be? That would be similar to fingerprinting all persons and keeping the print records in an FBI database. Just in case you'd ever commit a crime. Why stop there? We need tire tracks from every tire sold in America. So many crooks own cars or use them to get to the crime site.
What about shoe prints? Almost every criminal wears shoes while committing the crime? A shoe print database is necessary. What would the downside be?
What about hair samples? Saliva? Clothing fibers?
SHHHH don't give them any ideas....