A round is a single unfired unit of ammunition, like a bullet in a metallic cartridge, or shotgun pellets inside a plastic shell. The name may come from the fact that most ammunition cartridges are cylindrical and therefore appear round.
Prior to the use of self-contained rounds, the projectile and explosive charge were loaded separately, often in opposite ends of a firearm. This exposed the powder charge to the elements and made reloading awkward. The first fully integrated, breech loaded cartridge was made in 1808 by gunsmiths Jean Samuel Pauly and Fran?ois Pr?lat. In 1845, Louis Nicholas Flobert made the first metallic self-contained cartridge. It was essentially just a lead ball pressed into a percussion cap, but it was the precursor to all modern cartridges.