Thousands of crimes happen every year where intact brass and bullets are recovered at crime scenes. And a technology exists that allows manufacturers to encode a tracking number onto both, which can be then linked back to the person who bought the ammunition over the counter.
I propose that legislation similar to the Ammunition Accountability Act be introduced at the federal level, requiring over the counter ammunition to be encoded, and traced through a database, paid for by a 5 cent surcharge per round of ammunition sold. Sales and transfers of ammunition must be recorded. Purchasers must register for an ammunition license and be subjected to a background check. This won't create an undue burden on lawful shooters, but it will make criminals think twice before pulling the trigger.