Components of Ammunition


A single piece of ammunition comprises the bullet, casing, powder, and primer.


The metal projectile (usually lead) is expelled from the mouth of a firing cartridge.


A tube that holds all the other ammunition components together, typically made from brass. The bullet is usually held in the open end of the casing.


The gunpowder used in a cartridge that propels the bullet.


A small cap in the head of the cartridge that, when struck by the firing pin, ignites the powder.

How Does Firing Ammunition Work?

When you pull the trigger of a firearm, the firing pin hits the primer and ignites the powder. As the powder burns, it creates pressure that pushes the bullet down the barrel.

How Is Ammunition Measured?

Ammunition is measured by the bullet’s diameter, known as “caliber.” The caliber can be measured in both inches and millimeters (mm).

Ammunition is measured in millimeters or inches, depending on where it was invented. 9mm ammunition originates in Europe, whereas the .40 caliber was invented in the United States. Buy Safe Action System online.

Ammunition for a pistol corresponds to the pistol caliber so you will use 9mm Ammunition for a 9mm pistol.