Self defense, stopping power, and caliber, Part 3

Wednesday, April 02, 2008 Filed in: Ammunition, General gun stuff, Techniques & Training

(For convenience, you can access all the installments of this series at this link.)

Once it gets there, it has to do work.

In today's installment, we're going to look at the second of the Twin Tasks:

2) The bullet has to do rapid and significant damage to that thing when it arrives.

It may not be self evident, but kinetic (moving) energy is either used or conserved (stored.) In the case of a bullet, it starts being used simply by fighting the friction caused by traveling through the air. Unless it encounters a target, the bullet will use all of its energy in flight and gravity will pull it to the ground. We're interested in using that energy for lawful purposes before it's wasted in the atmosphere!

I usually refer to the second Task as "doing work", because that's exactly what is expected of the bullet. From the perspective of the target, the kinetic energy in a bullet can only do one of two things: it can be used to do work, or it can be wasted beyond the target.

(There is no such thing as an "energy dump" in a target, no matter how many times you see that nonsensical term. The energy does some sort of work, whether doing damage to tissue or pushing the bullet through the air. The bullet may use up all of the energy available, and stop inside the target, but it doesn't "dump" anything. The energy in such an event is depleted in expansion/deformation and in forward movement, both of which are work. Whether or not the work performed was useful to the goal depends on what it encountered along the way, which brings us back to the First Task.)

As the bullet traverses the target, its energy is used to push it through material more dense than the air it previously encountered. The amount of energy used in this endeavor is dependent upon the shape of the bullet; the more streamlined the projectile, the smaller the frontal profile, the less energy is expended in pushing it through the target. Conversely, the "flatter" the bullet profile, the more energy is necessary to move it through.

Think of a rowboat paddle - easy to move through the water edge first, much harder face first. If the bullet expands in the target, some of the energy is used to deform the bullet itself, and the rest is used to push the much larger, flatter profile through the target. In some cases, it uses up all its energy trying to get through the target and never makes it out the other side. This is why, as we touched on in Part 2, penetration can be controlled through the use of an expanding bullet.

At some point, we hope that the bullet finds something that the body deems necessary for function - and disrupts that functioning. That item could be structural (skeletal) - where disruption causes collapse; It could be electrical, where interruption of signals causes instantaneous nervous system malfunction; or it could be vascular (plumbing), where large leaks cause a loss of pressure that eventually results in unconsciousness.

Whichever system is compromised, the bullet needs to use some of its energy to do the necessary work of disruption. This is why I say that the bullet has to do rapid and significant damage to something when it arrives; if it gets there, but has so little energy left that it is incapable of inflicting necessary damage, then it might as well have not gotten there to begin with.

(This is not to suggest that the bullet's wound in such a case is benign or trivial! Remember, we have a task for that bullet to accomplish; if it doesn't do so in the necessary time frame, then it is useless to us. The classic example is the attacker shot with a .22 but still able to complete his assault. He might die of peritonitis a few days later, proving that the wound is not unimportant. However, it didn't complete our goal of stopping the criminal before he could harm an innocent, making it irrelevant to our situation. Keep the end in mind!)

Now that we understand the Twin Tasks, we'll take a look at the mechanisms by which all this might be accomplished. Until next time!

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-=[ Grant ]=-

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