How Does a Bullet Work?

What is a bullet?

A bullet is the projectile shot by a firearm. Typically these are made of iron or lead, but some non-lethal varieties are made from plastic or rubber. Bullets are commonly designated by two different types of measurements, calibre (referring to the width of the gun´s bore) or a millimeter measurement (refering to the width of the base of the bullet), and are sometimes used interchangeably. For example, the rifle bullets in .223 and .308 calibre are the same bullets as the 5.56mm and 7.62mm.

Cartridges

In modern firearms, all bullets come as part of a cartridge. Sometimes also called a "round," the cartridge is the combination of the bullet, the propellant, the propellant casing and the firing cap. The bullet itself is placed atop a brass casing that houses the propellant powder, and at the base of the cartridge is the firing cap.

How a Bullet is Fired

There is a wide variety of loading mechanisms in modern firearms, but all but the most experimental bullets are fired the same way. When the trigger is pulled, the firing pin penetrates the firing cap at the base of the cartridge, sending a spark into the propellant and igniting it. The resulting explosion drives the bullet down and out of the barrel at high speed. Rifling in the barrel imparts a spin on the bullet, giving it greater stability in flight.

Impact

Bullets do damage by imparting their kinetic energy onto the target. A large, heavy bullet traveling at high speed will do more damage than a small, light bullet traveling more slowly. This is why the mammoth .50 calibre round does substantially greater damage than the .45 calibre pistol round. Although the bore widths are similar, the .50 calibre round is a gigantic bullet propelled by a lot of propellant. Although large for a pistol round, the .45 calibre bullet is not as big and propelled by a much smaller charge. However, some bullets are designed to do greater damage to "soft targets" (human flesh and bone). The 5.56mm round of the M-16 rifle was designed to tumble in flight, thereby tearing the target up. "Dum dum" bullets have been cut so as to increase the chances of the bullet breaking apart on impact, causing a messier wound.