About Gunshot Wounds to the Head?

To understand gunshot wounds, it is a good idea to know a bit about bullets, which is not the correct technical term, as we shall see in a moment. The primary unit of a round of ammunition is called the cartridge, which consists of a casing, primer, and a projectile (bullet). The cartridge casing holds a propellant, often gunpowder, with the primer at the base of the casing and the projectile at the top. When the firing pin of the gun strikes the primer, an explosion lights the gunpowder causing rapidly expanding gases to propel the bullet out of the barrel of the gun.

Bullets are identified by their diameter and are designated either in the metric system (i.e.g., 9mm) or in the English system (.22 or .380). The caliber of the bullet that is used in a particular weapon is also the designation for the type of gun (i.e., a 9mm pistol). Forensic specialists categorize bullets as small (.22 or .25), medium (.32 or 9mm), or large (.40 or .45). 

Entrance wounds are usually round in shape. Wounds into skull bone often produce coning of the bone at the surface that spreads away from the weapon; with the tip of the cone pointing in the direction where the gun was fired. In thin areas of bone, like the temple, you may not see coning. A small, dense projectile could push out a rounded part of skull, while a larger projectile may produce circumferential fractures that would radiate away from the point of entrance. At close range, gases from the firing of the cartridge can cause the entrance wound to stretch and tear.

Exit wounds vary in shape: round, crescent, slit-like, or oval. It is a misconception that exit wounds are larger than the entrance. Exit wounds are more irregular and emit more blood than entrance wounds because the projectile has expanded or tumbled along its trajectory and bone fragments may have been forced out through the skin.