If you’re not knowledgeable in the firearms department, ammunition can be a daunting subject. Choosing the right ammunition for your firearms, whether hunting or personal defense, is an important decision. Having the proper ammunition is essential to keeping your firearm safe while performing at its best. This topic can be overwhelming and confusing, but we’ve made it simple for you. Ammunition is generally specified to some extent. The United States commercial market uses a US standard measurement, while most of the world uses a metric system. Measurements in metrics are almost always a “diameter to length” ratio. For example: 5.56×45mm is 5.56mm wide and 45mm long. Shotshells are measured with a “gauge”, a lower number has a larger diameter. For example: A typical 12 gauge barrel is 70mm long, which is calculated as 2½”. Parts of a Cartridge A cartridge consists of four components; cartridge case, ignition fuse, gunpowder/propellant and bullet. 1. Sleeve Sleeves are typically made of brass, nickel or steel. 2. Ignition Wick

This is the round hole in the base of the cartridge that fires the propellant.

Gunpowder/Propeller
It is the part where the gunpowder is located.

Bullet
Types of Bullets

Round nose lead (Lead Round Nose, LRN)
Paper cutter (Wad Cutter, WC)
Semi-paper cutter (Semi Wad Cutter, SWC)
Semi-jacketed (Semi-Jacketed, SJ)
Full metal jacket (Full Metal Jacket, FMJ)
Semi-jacketed hollow point (Semi-Jacketed Hollow Point, SJHP)
Sheathed hollow point (Jacketed Hollow Point, JHP)
Private (RCBD)
Besides the most common shells, there are a few additional varieties to consider:

Soft Point (SP): This type of bullet is open-ended.

Armor Piercing (AP): The core consists of steel alloy instead of lead. Also called armor piercing.

Boat Tail (BT): The rear end of the cartridge is tapered to stabilize flight.

Boat Tail Hollow Point (BTHP): It is a hollow-tipped Boat Tail projectile.