Finger or thumb print is the thing for now along with every other form of identification you have.

I can not figure what the hell good it'll do.

It's possible to tell who made a bullet but not which box it was in or which retailer sold it.

Besides criminals don't follow laws.

Jahn has it right. It isn't a matter of tracking the ammunition in order to link it to a possible crime. It is a matter of identifying who has ammo and in what quantity. This of course gives record of any guns that the purchaser might own as well, thus creating a record of ownership...somewhere. Given that there are a large number of unregistered guns out there then this would give the ptb the tools that they need to find unregistered firearms. I have my share. Legal yes, but not registered. However I really have nothing to hide.