Cartridge

Often referred to as a round, and frequently (but incorrectly) as a bullet (projectile), cartridge is a term used to describe rifle or handgun ammunition. The cartridge is made up of a bullet, case, powder, and primer. After pulling the trigger, the only part of the cartridge that is released down the barrel is the powder and bullet. The cartridge case, including spent primer, is expelled through the ejection port or otherwise removed manually from the chamber.  There are two main types of cartridges: rimfire and centerfire. Rimfire cartridges have primer material that is placed on the inside bottom rim of the case. The firing pin strikes the rim detonating the primer, which then ignites the powder (some .17 and 22 calibers are rimfire). In centerfire cartridges, the primer is a separate component located in the center of the case head. This system is highly reliable and therefore virtually all modern handgun, rifle, and shotgun ammunition is centerfire. With proper precautions, this ammunition can also be reloaded.