Cartridge

From GunCounter

A Cartridge (aka a Round) of ammunition is a fully self contained unit made up of a bullet, case, primer and powder. When using modern, metallic cased ammunition, you load “cartridges” or “rounds” or just “ammunition/ammo” into your firearm.

Note: Blackpowder/muzzle loading firearms do not use cartridges, and you do, in fact, often load the bullet separately, after loading the powder. But this does not apply to modern firearms used by most people for hunting, self defense or in the military.