Shot Placement and Energy Transfer
In previous blog posts I have mentioned what I consider the King and Queen of Combat Marksmanship. The King is shot placement and the Queen is energy transfer. Shot placement is self-explanatory, it is where the bullet strikes, enters, transitions though, and exits the target. Energy transfer is more particular. It is a component of terminal ballistics. I could have said terminal ballistics. A discussion about terminal ballistics is not a can of worms. A discussion about terminal ballistics is a 55 gallon drum of soul sucking carnivorous leeches, that causes PhDs in engineering to break out in fistfights and remove each other from Christmas cards lists.
For all of the blog posts I try to keep them pretty basic. There will be finer points that will be left out. There will be certain details glossed over. It is my intent to keep the conversation middle of the road. If you have PhD and you work at Picatinny, this will not be a peer reviewed technical dissertation. I am always learning myself.
Energy transfer describes the rate and amount of energy transferred into the target. This means that when the bullet hits the target that not all projectiles act the same. That as the projectile moves in the body of the target they transmit different amounts of energy at different times. Some projectiles will penetrate deeply and then begin to transmit their peak amount of energy. Others will begin to transmit energy early in their path. Others may transmit very little of their energy into the target.
The ability for a projectile to transfer adequate energy into the target is key. The ability to transmit most of this energy into the vital organs is ideal. The ability to transmit the maximum amount of energy across the entire path of travel is optimal. This is dependent on projectile size, shape, material, and construction. I will refrain from getting into that here.
I define energy as whatever property that must be transmitted to an object, to perform an effect on the object. We all know about kinetic energy of the bullet. But the amount of force it exerts inside the target is important. The key is the rate this energy is exerted. Force is an interaction that changes the motion of an object. Force is applied by the projectile against the tissue of the target or against the materials in the armor. The force applied by the projectile against the tissue creates a permanent and temporary hollow space inside the body. This is called cavitation.
Cavitation is basically boring a tunnel inside the body of a target. That the force exerted by the projectile displaces tissue. It forcefully plows a hole, sometimes much larger than the projectile through the target. Some projectiles cause large amounts of cavitation at different peak points in their path through the target.
Cavitation in solid organs such as the heart, brain, and large vessels such as the Aorta or Vena Cava, is incredibly lethal. These tissues are effectively torn apart by the force transmitted that was caused by cavitation. Projectiles that penetrate and cause massive disruption via cavitation, cause damage that solid organs and vessels cannot recuperate from. This damage if extensive enough it is instantly lethal.
So lethality is tied to cavitation. Cavitation results from the force exerted against the tissue. Force exerted against the tissue results from the projectiles ability to transfer energy. This is why energy transfer is the queen of combat marksmanship.
There is a reason shot placement is the king of combat marksmanship, as it wears the pants in the relationship. Simply put a .22 caliber bullet placed in the right spot is lethal. When working as medic, I worked the scene of a shooting. I found out later, the story was that there was a drug deal and the buyer wanted the drugs and money. While he was running away he fired one shot over his shoulder, with a .22 Raven.
I conducted a rapid exam of the patient, the seller. He was pale white, warm to the touch, apneic, and pulseless. There were no obvious entry wounds, exit wounds, and there was no blood. There was no blood on him or the ground. There was an organized cardiac rhythm under the CPR, otherwise known as PEA. This means I need to resolve the 4T’s and 4H’s of PEA. One of the T’s is Cardiac Tamponade.
This is resolved by executing peri-cardiocentesis, where a long needle is inserted into the sac that surrounds the heart. This condition can stop the heart if it is filled with blood from injury. So I press down on the patient’s upper most abdomen, insert the needle by his xyphoid process, aim towards the heart and watch the monitor, while CPR is paused. The PEA is interrupted by the contact with the needle and I feel pressure. I am at the heart. I draw back on the syringe and no blood. I re-advance the needle and draw again, nothing. On the third try, I am drawing back when I am well away from the heart. The syringe now has blood in it.
I then percuss his chest, its full of fluid, its full of his blood. Then I see the entry wound. It had been covered during CPR. It was a small entry wound along the left margin of the patients sternum, smaller than a mosquito bite. The 22. Round had entered just off his sternum, in the 4th inter-coastal space. He was dead within seconds.
This is a case in point that even the smallest calibers can cause the destruction of vital organs. That large cavitation, fragmentation, and secondary wound channels all take a back seat to where the projectile goes. What the projectile hits on its path is more important than how it hits. Some projectiles will begin to deform very early, or late, or completely, or not at all. This does not matter if the great vessels, heart, brain, and other vital organs are hit.
Now I do not want anyone thinking I am being contradictory. There still is no replacement for displacement. That larger bullets, with higher ballistic co-efficients, that are designed to have better energy transfer (and therefore cavitation) will have a higher probability of killing the same target with the same point of impact.
Again, some projectiles will begin to deform very early, or late, or completely, or not at all. If they destroy vital organs because of where the projectile travels, it really doesn’t matter.
So we have clearly stated what is optimal, a high BC projectile placed into vital organs. But what happens when the shot is not placed into vital organs, what happens when the aim is off by just a bit. This is complicated by the type of tissue that the projectile is moving through.
Bone and Skeletal Muscle can absorb, deform, and deflect the projectile. Wounds to skeletal muscle and bone may be incapacitating but are not normally lethal. Softer tissues like the lungs and intestines will suffer massive damaged but will allow projectiles to pass right through. A collapsed lung can result in air and blood trapping (Hemo/ Pneumothorax) that can be lethal if not corrected. Solid organs like the Liver, Pancreas, and Kidneys will tear and rupture. These can be non-field repairable and result in eventual death. Vitals organs such as the great vessels, brain, and heart will rupture in very much the same manner.
There are circumstances when the aim is off and the direct wounding of the projectile or the permanent wound channel, is not lethal. Yet, the temporary wound cavity from cavitation is lethal. The temporary wound cavity is caused by the cavitation which is we have stated is based off the projectiles ability to transfer energy. This varies by caliber and bullet composition (a series of blog posts in their own right).
The basics of what happens is that as the projectile bores through the target. As it travels the projectile, and if applicable, its fragments, tears direct holes into the target. If the projectile does not result in lethal injuries the energy it transfers can. The energy this (these) projectiles transfers and the rate at which it is transferred it is directly result in the cavitation pattern. This cavitation pattern and the force it applies can destroy vital organs. This is a critical component in how lethal a projectile is.
This is why I call energy transfer the queen. Like any good queen, she magnifies the king’s power. She subtly but substantially influences the environment. She expands his reach, she makes him stronger. Again, shot placement is the king for a reason. Everything you do supports where the shot is placed. Just in case the king is a touch off target, the queen has his back.
The next blog post well cover Suppressors and the SCAR.