Ballistics of Gunshot Wounds

A bullet is a carrier of force, and the energy that it dissipates within the body causes the injuries. The characteristics and severity of a gunshot wound are determined by the design of the weapon and projectile, the intermediate targets the projectile encounters between the gun muzzle and the body, and the sequence of tissues encountered along the projectile path.

Two major mechanisms of wounding occur. Briefly, they are:

Crushing of the tissue struck by the projectile

This results in formation of a permanent cavity, and depends on:

1. Characteristics of the bullet, for example

a) Soft-point and hollow-point bullets deform into a mushroom shape when striking soft tissue. This increases surface area and wound severity.

b) Velocity - Low velocity bullets (produced by shorter barrelled guns) may not induce mushrooming after impact, thus causing less damage.

and

2. Bullet fragmentation

a) This increases surface area, and much more tissue is crushed.

b) Multiple perforations weaken tissue and create focal points for stress, which are particularly vulnerable to the effect of temporary cavitation.

c) Bone being dense, absorbs more force and may splinter, causing further damage as secondary projectiles.

Radial stretching of the projectile path walls

It results in the formation of a temporary cavity due to tissue stretch. Less elastic tissue (e.g., brain, liver, or spleen), fluid-filled organs (including the heart, bladder, or gastrointestinal tract), and dense tissue (e.g., bone) may be damaged severely. More elastic tissue (e.g., skeletal muscle) and lower-density elastic tissue (e.g., lung) are less affected by the formation of a temporary cavity. A lighter, faster bullet is likely to be used up forming a larger temporary cavity, but leaves a smaller permanent cavity.

Lastly, if a bullet creates an exit wound, it generally indicates less damage as compared to a bullet that stays in the body (and transfers all of its kinetic energy).

References:
1. Gunshot Wounds: 1. Bullets, Ballistics, and Mechanisms of Injury
Jeremy J. Hollerman,1 Martin L. Fackler,2 Douglas M. CoIdwelI,3 and Yoram Ben-Menach
2. Where's the best place to take a bullet if you get shot?  Josh Clark
3. Wound Ballistics and Tissue Damage; Nimrod Rozen and Israel Dudkiewicz

 

This post from Sana Shaikh, MS4