A fired bullet and cartridge case

A fired bullet with rifling impressions from the barrel of a gun (left). A fired cartridge case and fired bullet (right). Experts can often identify the weapon used based on rifling impressions on the bullet, or breech face and firing pin impressions in the primer at the base of the cartridge case.

How the Rifle and Handgun Fire

Essentials of Forensic Ballistics

MidiaNews Laudo aponta que arma trazida por intermediário matou advogado

Cartridge Cases - Hornady Manufacturing, Inc

How do coroner or forensic people know which bullet hit someone first, second, or third when someone has been shot multiple times? - Quora

How do coroner or forensic people know which bullet hit someone first, second, or third when someone has been shot multiple times? - Quora

Cartridge Case Identification

Ammunition 101: Understanding the Basics of a Firearm Cartridge [or Bullet] - Dark Earth Tactical

Would it be possible to fire guns before sold and scan the bullets and casings into a computer database and then automatically know what gun casings and bullets came from when found