Not all the explosive wounds were caused by gunpowder-filled musket shells. Little understood at the time, though recent research has shed some light on the subject, was the existence of a temporary wound cavity of enormous proportions during the passage of the bullet. This temporary cavity was caused by a transfer of energy from the bullet point tangent to the body, to the fluids of the body. Since water is incompressible, the result is to accelerate the water, hence the flesh, rapidly away from the projectile due to the lighter inertia of the body tissue. This energy imparted to the tissue caused development of a cavity which expanded to many times the size of the bullet, flexing several times as the elasticity of the muscle fibers tried to restrict the cavity against the force of the energy-transferred fluids. The effect was to cause a secondary rending and tearing of the flesh. The passing of the bullet excavated, by physically destroying flesh equal to the diameter of the bullet
The complete story of Federal and Confederate small arms: design manufacture, identification, procurement, issue, employment, effectiveness, and postwar disposal. By WILLIAM B. EDWARDS