Physiological Principles

The physical principle behind killing with free projectiles is the transfer of high levels of kinetic energy (the energy of movement) in an extremely short time from the projectile to the animal’s brain. If the correct type of projectile is used, the resulting damage should be sufficient to kill the animal outright. Kinetic energy (KE) is a product of half the mass (m) of an object and the square of its velocity (v). it is expressed by the following formula:

KE = ½mv²

The effect of the above relationship on the muzzle energy of a projectile is shown in Table 1. Muzzle energy is expressed in joules (J), mass is expressed in kilograms (kg) and muzzle velocity in metres per second (ms¯¹). In these examples the mass of the projectile in both cases is 5.51g and the muzzle energy required for an effective kill is 200 J. 

Table 1 Relationship between mass, velocity and muzzle energy of a free projectile

It can be seen from Table 1 that a decrease of a little over 25 percent in muzzle velocity reduces the muzzle energy by nearly 50 percent, leaving it well below the effective kill level. Therefore, it is imperative to use a sufficiently powerful charge to propel the projectile at the optimum velocity. Any factor which impairs the velocity of a projectile, such as an underpowered charge, will have the effect of reducing its muzzle energy, with consequent implications for animal welfare.

Next: Physiological Effects