Q: It seems universally taken as gospel that the efficient killing of deer-size animals requires a striking energy of at least 1000ft-lb (call it 1400 Joules in modern parlance — Ed), and larger cervus such as sambar, wapiti and moose require at least 1500ft-lb (say, 2000 joules — Ed) of striking energy. But another important factor seldom gets a mention.
Energy is only half of the equation, since it has also been determined that in the normal take-’em-as-you-find-’em kind of hunting, reliable penetration of deer-size animals requires that the bullet strike with a momentum figure equivalent to 240,000 arbitrary units as calculated by multiplying the bullet’s weight in grains by the striking velocity in feet per second.
Larger game such as moose and sambar, when taken “as they come” require at least 360,000 of these same relative momentum units.
How would you describe optimum bullet performance in layman’s terms?
Guy Neville
A: Most reliable observers of killing power have concluded that kinetic energy determines a bullet’s total destructive ability in volume of tissue destroyed while momentum is one of the chief determinants of penetration, assuming that the bullet’s construction is suited to the size of the game.
Roughly speaking, therefore, the bullet’s momentum determines the depth of the wound, while its kinetic energy determines the extent (or volume) of the wound channel.
A bullet lacking only in energy may completely penetrate the animal, with little tissue destruction, and allow the stricken animal to run a long way before dropping, then survive the wound and recover.
A high-energy, low-momentum bullet, on the other hand, will destroy a lot of tissue but only to a comparatively shallow depth. Such a bullet usually kills spectacularly when placed in the lungs, for instance, but often fails miserably when heavy bones or thick shoulder, neck or rump muscles are encountered on the way in.
There’s no question that penetration is a function of momentum, and penetration operates to alter or modify the shape of the wound.
Low momentum results in a relatively shallow wound; high momentum produces a deep wound, although with a given striking energy the identical amount of tissue will be destroyed with either type of wound.
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