Lawmakers are pushing a new technology to help trace hand-guns used in crimes. It's called 'microstamping.' It's essentially a license plate for handguns that is difficult to remove. It's almost like a rubber stamp, but it's inside the gun and it microscopically stamps the ammunition cartridge. When an ammunition cartridge is ejected from a semi-automatic handgun, it carries a distinguishing mark made by the firing pin. And from those TV cop shows, you probably know... (GunPolicy.org)