Establish and require that all firearm ammunition be registered into a newly formed National Firearm Ammunition Purchase Registry (NFAPR). This would track all ammunition sale across the US (50 states and all territories) and require that all ammunition vendors obtain and log into such a registry the name, address, total number of rounds, ammunition caliber of purchasers of ammunition. This would be then kept in a database managed by the USDOJ and ATF.
This registry will ensure that all ammunition can be tracked to an owner and perhaps prevent unlawful users of ammunition from purchasing ammo as they now would be identified.