Cartridges are the proper term for the combination of bullet, casing, gunpowder, and primer. When you go to the store to buy ammo, this is what you are purchasing. Each cartridge type has a name that is based (sometimes loosely) on the caliber of the bullet it uses, and usually has a few descriptors after it to help distinguish it from similar rounds. These descriptors can include casing length, casing diameter, overall cartridge length, the year it was invented, the company it was originally designed by, etc... The list goes on.
Cartridges are somewhat hard to explain especially to someone without any prior firearms experience. The best way to learn about them is to try and understand what ammunition goes with what firearm, and learn why a particular round was given its name. To help you with that, I am going to give some common examples of some popular cartridges and explain why they are called what they are. For a full listing of popular cartridges and what they are used in/for please see our cartridge table.
||A box of ammunition
Here is a sample cartridge you may buy in the store. I added the full name, and I'll explain what everything means:
Federal 124 grain 9mm Parabellum JHP
What does this mean? This is a 9mm Parabellum (standard 9x19mm pistol round) round. It uses a 124grain (weight) Jacketed Hollow Point bullet, and is made by Federal, a common ammunition manufacturer.
The .45 ACP is the standard cartridge used in .45 Caliber semi-automatic pistols. ACP stands for Automatic Colt Pistol, as it was originally designed for use with the Colt semi-automatic pistol and the M1911. The name of this round is often shortened to just 45's. (e.g. 'Can I get a box of 45's')
The .223 Remington was developed as an enlarged version of the .222 Remington Cartridge for use in the Armalite AR-15 Rifle which would later be adopted by the U.S. Military as the M16. Although the projectile is actually .224 inches in diameter, it is called the .223 after its .222 predecessor.
The 5.56x45mm NATO round is based on the .223 Remington round. When the M16 was picked up by the military, they made the round it fires a little more robust, giving it a thicker casing and more powder. Firearms chambered to use the 5.56x45mm round can use .223 Remington as well. However, .223 firearms cannot use 5.56's, due to their greater pressure.
The .30-06 Springfield round gets its name from being a .30 caliber (0.3 inches 7.62mm) round that was invented in 1906 (06 or aught-six). The M1903 Springfield Rifle was modified to use the new round.