make a law requiring all gunstores to shoot the gun and submit the bullet for a national database

All guns have unique barrels, when a gun is shot an imprint of this is left on the bullet almost like a finger print. (in that no two are the same) There should be a law reqiring all gun sales that take place at stores to shoot the gun and submit the bullet to a national database. Imagine the advantage law enforcement would gain if any bullet they found could be submitted for instant results, to find out what gun shot the bullet, who the owner is and where they live. Having acess to a fingerprint database was the biggest breakthrough in modern crime enforcement, I mearly suggest we create one for the tools the crimes are comitted with.