For those with only a working knowledge of firearms, there may be some confusion about the terms bullet, ammo (ammunition), round and cartridge. The term round or cartridge refers to the entire package of bullet, casing, powder/propellant, rim and primer. Ammunition is the plural of rounds/cartridges. Bullet only refers to the solid projectile (tip) propelled from the end of the cartridge when the gun is fired. There is an excellent photo breaking this down at guntoters.com.