Kevin at The Smallest Minority has a great post up on Firearms/ammo "fingerprinting" and why it's a program that shouldn't be enacted in law....for the best of reasons; it just DOESN'T work.
Where it has been enacted, it is a program that has cost upwards of $16 Million dollars, without a SINGLE crime having been solved. The technology doesn't work, can be easily fooled, and is a massive drain on scarce law enforcement resources. Let's just hope the politicians have the sense to stop throwing money down a rathole.