The penetration of a projectile(bullet or fragment) into tissue is categorized as a special form of blunt trauma.
A gunshot wound consists of:
- tissue penetration,
- crushing and rupturing of tissue,muscle, capillaries, nerves and bones(depending on size and density),
- the formation of a primary cavity or more accurately a permanent wound tract or channel,
- the formation of a secondary cavity and
- for close range shots, greater injury as a result of the blast effect from the bullet’s propellant gases. If the bullet is retained, tissue burning takes place.
The movement of the projectile through tissue follows fluid dynamics, a complex engineering topic. The immersed projectile is considered to be moving forward with surrounding tissue “flowing” around it.
The chances of survival depend on the nature of the injury. This in turn depends on how deep was penetration, the type of gun and bullet, the distance, the type of tissue into which the bullet entered, the degree of “yawing” and tumbling of the bullet as well as the amount of blood lost before the victim is treated.
Here is an illustration of the mechanism of a bullet wound for one type of bullet.