This is the third part of our study on ballistics. First, we looked at interior ballistics which is what happens when the shooter fires and the bullet is still in the gun. After that, we briefly examined exterior ballistics, which is what happens once the bullet leaves the muzzle of the gun and the forces that act on it as it travels to the target. Now we will look at terminal ballistics. This is what happens once the bullet arrives at the intended destination. Terminal ballistics is the study of what a bullet does when it impacts a target that is either animate or inanimate. Terminal does not specifically mean killing something. While death may be a result, our study is not limited to just that outcome. When correctly defined, terminal means the end of a process or series of events. What does the bullet do when it strikes its target? Does the bullet expand or remain pristine? Does the bullet penetrate or just impact the surface? Does the bullet do too much damage to the target? These are all part of the study of terminal ballistics, which is simply the target’s affect attained by the bullet.
The study of terminal ballistics has varied over the years. At one time, it was politically incorrect to say that the goal was to determine the best bullet to kill an animate object. However, this is the very goal hunters are trying to achieve on their intended target. On human targets, the goal is to incapacitate as quickly as possible during a self-defense situation. The ability to get the person to cease whatever action it was that made you choose the ultimate course of reaction. Incapacitation needs to occur with as few shots as possible. In a military or law enforcement setting they are not limited to just a personal self-defense situation. However, the goal is still the same—to render the target incapable of further action as quickly as possible.
To achieve this goal we need a good transfer of energy from the bullet to the target. This is the core of terminal ballistics. This energy transfers when the bullet is in contact with or passing through the target. Once the bullet exits or stops in the body cavity, all transference of energy has ceased. The remaining energy is lost when the projectile exits after passing through the target.
In a civilian self-defense situation, remaining energy is not a good result if the bullet’s objective was to incapacitate the target with as few shots as possible. Moreover, in this situation we do not want a bullet with unspent energy hitting anything other than the chosen target. Military objectives may be different as the goal is to incapacitate as many opposing troops as possible. A bullet with remaining energy is free to continue and strike additional targets. In terminal ballistics, this is the study of penetration.
When a bullet penetrates an animate target, such as a human or animal, it can display some strange reactions. These are dependent on where the bullet hits and what type of bullet is used. A fully jacketed bullet may have great penetration, but may cause very little energy transfer as it usually does not expand or fracture. A soft-nose or hollow-point bullet may have great expansion but may have trouble penetrating the target if it encounters obstructions. Incredibly, these obstructions do include clothing. When they hit denim clothing, handgun bullets have serious trouble expanding correctly. While this does not cause clothing to be in any way bulletproof, it does have a drastic effect on most defensive loads. Ideally, at least six to nine inches of penetration is the desired amount for self-defense rounds.
As the bullet moves through the cavity, it will create both a permanent and temporary cavity due to a shock wave. The result of the temporary cavity can be very devastating since some internal organs are not flexible. If the projectile strikes bone, innumerable variables can occur. The bullet may pass through the bone, completely change its trajectory, break into fragments, or even explode which creates additional cavities.
Terminal ballistics is the study of kinetic energy transfer, penetration, and incapacitation of the target. Ammunition companies and re-loaders study this science to determine the best projectile to accomplish a given task. Ultimately, it does not come down to the firearm, shooters skills, or the years of practice. The action and reaction of the target cavity that the bullet strikes will determine the outcome of a defensive situation.