Derecho

Terminal/Wound Ballistics and Distance of Firing

7

This chapter deals with what takes place when the bullet, missile, or shotgun pellets strike the target, which can constitute living tissue or some other material. During this brief period of interaction the missile tends to suffer some degree of deformation, or disintegrates, and the target is pierced or otherwise damaged. The degree ofdestruction which takes place is dependent upon the mass of the projectile, its striking velocity, its design and construction and the nature of the target. Much has been written upon what a bullet or shot charge will do upon a human target, even to the degree of stating the precise volume of the anticipated temporary cavity or the quantity of haemorrhagic tissue which will be found within the woundtrack for each unit of kinetic energy expended by the bullet. However, over the years I have seen so many atypical or, some would say, freak effects, that I would hesitate to predict exactly how a missile will perform beyond stating generalisms. The human body is not a homogeneous block of material such as that typified by a block of 10% ordnance gelatine. In reality it contains hard bonesexhibiting curved surfaces which can deflect a bullet or cause it to break up at velocity levels where one would expect penetration. Fatty tissue or liver will not offer the same resistance as would muscle. The lungs constitute a cavity within the body filled with air, which, in contrast to the tissue surrounding it, is compressible. On top of all this there is an overlying tendency for the unexpected tohappen during these extremely brief, sometimes high-energy change interactions, which at times has caused me to wonder what exactly constitutes normality. A bullet can be deflected off a rib on a person’s back so it is directed along a circular path in the tissue covering the rib cage leaving the victim with a relatively trivial injury. A bullet can be deflected or break up on striking a relativelymodest item of screening cover interposed between

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the firer and the intended victim, or some article inside a pocket of the coat worn by the victim. A heavy sheepskin coat and sweater can greatly reduce the lethal capabilities of a charge of birdshot fired from a shotgun even from a relatively short distance. A man can die after being struck by a low-energy airrifle pellet, if it chances to strike a vulnerable exposed part of his body, while another man can survive extensive injuries to the body and head inflicted by a high-powered rifle or sawn-off shotgun. You can go to a scene of a suicide where the victim has placed the muzzle end of a 12-bore gun under his chin before firing it, and find the shot charge and wadding lodged inside his head during thepost-mortem examination, rather than the more usual explosive type of injury from such a discharge. However, much work has been done by other researchers, who do not always concur with each other’s findings, which I will attempt to cover later in this chapter.

7.1 Mass, Momentum and Kinetic Energy
This section attempts to address the misconceptions concerning the actual meaning of the above terms.The expression ‘mass’ is frequently confused with the expression ‘weight’. Debate concerning the other two terms, when attempting to predict the potential of a moving object to influence other bodies, can be traced back to the seventeenth century when a protracted controversy took place between two eminent mathematicians, Liebnitz and Descartes. The curious property under discussion was given therather vague title ‘the efficacy of moving bodies’. The great dispute arose because each attributed to it a different meaning. Liebnitz maintained that the efficiacy of a moving body was its Kinetic Energy, or its capacity to do work. Kinetic energy is energy associated with motion. He maintained that this kinetic energy was proportional to the square of the velocity of the body. He was of course...