How do determine what bullet came out of what gun?
Firearm Examiners use microscopic marks on the surfaces of bullets and cartridge case to match them to each other. The microscopic marks are caused by the little imperfections on the surface of the breech face and barrel of a firearm caused by the tools used to make those parts in the factory. The shapes of the imperfections on the breech face are stamped on the cartridge case under the intense pressure caused by the powder igniting. The imperfections in the barrel cause scratches on the bullet as it passes along the barrel being pushed from behind by the exploding powder.
