As another responsible gun owner, I see absolutely no problem with ballistic fingerprinting. The fact that a file exists showing what a bullet shot through, or a cartridge casing ejected from a gun looks like should mean absolutely nothing to me as long as I'm using the gun in a legal fashion. The fact that the data does exist would certainly make me think twice before using it in an illegal fashion.

How much good it would actually do, though, I'm not so sure. It would not stop anyone who is determined to use a gun in a crime. In fact, most guns used in crimes have either been stolen or passed through so many hands that being able to link a bullet to a particular gun to its original purchaser is still a dead end. And many of the folks into precision shooting (as, presumably, the current sniper is) may have modified their guns so much that the original ballistic data would be meaningless. And then, there are always shotguns that don't leave any ballistic evidence unless you're dumb enough to leave a shell casing lying around. Even so, I still think it's a good idea.