Compel gun manufacturers to generate and register a ballistics specimen with the Serial Number of each weapon.

When some one is shot, the ballistics of the "slug" is only significant if the weapon is found. By registering the Ballistics to a serial number, the owner of that weapon can be determined. This will help identify people faster and saving time and money during an investigation. Obviously weapons purchased through a black market may not indicate the "shooter" but by tracking to the registered owner, a custodial trail may be determined.
This is also a deterrent to weapon owners who shoot indiscriminately and cause harm to people and property.