Terminal.jpg
An Example Plot of the Wound Profile for a Conventional Bullet
Terminal Ballistics

Terminal Ballistics refers to the interaction between a bullet and its target. The behavior of bullets on impact is largely the consistent depending on the material that it impacts. In a practical sense, the science of terminal ballistics is most often used in the design of bullets for different purposes. In a forensic sense, this can be useful as these different designs of bullet will leave different damage patterns, and are therefore easily identifiable.

There are three basic classes of bullet:
  • those designed for maximum accuracy at varying ranges;
  • those designed to maximize damage to a target by penetrating as deeply as possible;
  • those designed to maximize damage to a target by deforming to control the depth to which the bullet penetrates.

Bullets designed for maximum accuracy will be manufactured with a focus on aerodynamic stability. This is achieved with a hollow-point design (having a hollow cavity in the tip of the bullet), to place the centre of gravity towards the back of the bullet. Further, enhanced rifling in the barrel of the gun will help greatly with accuracy.
Bullets manufactured to increase penetration are usually made with a lead core and a copper, brass, or mild steel jacket. This helps to maintain the shape of the bullet on impact so as to transfer as much momentum as possible into as small an area as possible. These are also usually fired at a slightly lower velocity in order to decrease wound radius (as shown in the diagram).
Expanding and fragmenting bullets are used in order to control penetration depth, in order to create maximum damage. Expanding bullets use a lead core, with a jacket that doesn't extend all the way to the tip. This has the effect of allowing the bullet to "mushroom" on contact, spreading out and causing a wound cavity almost twice the calibre of the original round. Fragmenting bullets are made with a deliberately low integrity metal jacket, meaning that on impact, the bullet will shatter and cause wider damage as the fragments disperse.

Sources:
"Shooting holes in wounding theories: The mechanics of terminal ballistics.", http://www.rathcoombe.net/sci-tech/ballistics/modeling.html (1/10/2009)
Dodd, Malcolm J., Terminal Ballistics, Taylor and Francis, 2006
Graph from http://www.rathcoombe.net/sci-tech/ballistics/modeling.html