Every firearm leaves a distinct "print" on a bullet when fired.
Moving forward, every firearm made; will have a bullet imprint stored from the manufacturer before being sold.
The "archive" can only to be accessed by court order. IE search warrant. Only bullets used in crime scenes can be submitted. Also allow 1 year for all gun owners to submit a fired bullet for each gun owned, to the archive. Anyone caught with a gun that has a bullet archived from a crime scene gets life in prison. Anyone accessing the archives without a court order gets life in prison. Example: Colt makes a firearm. Bullet is fired and stored by manufacturer. Gun is sold to Mr. Nuetral. He robs a store and fires warning shot. Bullet is retrieved and matched to archive. Mr. Nuetral goes to jail for life.