The main thing really wrong with this idea is that it’s totally unworkable. If you want to spend a few hundred million directly in building this, and a few billion in indirect costs, in order to make yourself feel like you’ve ‘done something’, then maybe it has value.
As a law enforcement tool, it’s totally worthless.
So let’s say this system is in place. There are photos on file of 100 million gun signatures. You arrest a subject, and take a ballistic fingerprint of his gun.
How in hell are you going to match it against 100 million signatures? Gonna put an army of ballistics experts to work for a couple of years to find one signature?
If you’re expecting computers to do the matching, I think that’s highly unlikely. It’s taken us a couple of decades of work to get fingerprint matching relatively accurate. Ballistic signatures are much different, because they are ‘fuzzy’. You don’t get exact matches - after each bullet is fired out of a gun, the signature changes subtly. After a few years, I doubt you could make a match at all, even by visual examination.
This is just yet another huge bureaucracy that would be totally ineffective and very expensive.
Here in Canada, we have recent experience with such ‘feel-good’ legislation. We now have a national ‘gun registry’. Everyone is supposed to have their guns registered with the government. This is much simpler than the ballistic fingerprinting idea - it’s just a big database of gun serial numbers and owners.
Several years after it was made law, it has an extremely low rate of acceptance - many gun owners are simply ignoring it. Plus, the database is apparently broken, police departments are screwing up the records by accident, there is no funding for local jurisdictions to manage it, etc. It’s a mess. And I don’t believe it has been helpful in solving a single crime. Because, as you might guess, the people who commit crimes with guns tend to not volunteer them for registration. Nor will they volunteer them for ballistic fingerprinting.
And if they’re using a gun that has been ‘fingerprinted’, you can bet the first thing they are going to do is take a wire brush to the inside of the barrel and modify the extractor and firing pin to make a match impossible. And you can bet that detailed instructions for doing that will be on the internet within hours of such a law passing, if it’s not there now.