Cartridge (firearms)

type of ammunition packaging that includes a bullet or shot, a propellant substance, and a primer within a metallic, paper, or plastic case

A cartridge (also called a round, sometimes a shell) is a type of ammunition, consisting of a cylindrical casing (made of metal, usually brass) that has inside of it a bullet, gunpowder and primer. It is made to fit neatly in the chamber of a gun. This kind of cartridge became usual in the 19th century.