human fingerprints are almost permanent,so called gun "fingerprints' are just machine marks left when the barrel is broached and will change over time depending on what goes down the barrel, cleaning brush, hard jacketed bullets , rust , even lead bullets will wear it some and change the markings , you could also polish the bore or even change it.
to take a "fingerprint " at the factory and creat a huge data base would only be marginely effective.
way it is now , if the police find the gun right after the crime and have enough of the bullet left to read any markings they some times can make a match.
to take "fingerprints " of guns at the factory is not a magic bullet to stop crime , it's just one more "feel good" law that wont work, BUT it will create a data base of guns and gun owners, some thing that liberals and dictators love to have.
44MAG