Mechanics of Terminal Ballistics.

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mrsirr

FNG / Fresh Meat
Apr 12, 2013
4,077
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Over here, no not there, here.
Warning, this is a long post, I'm not abridging it because I want to be very very clear. If you aren't into this kindof thing this article probably won't make you a fanatic. Although this is a good place to get a pretty good run-down if you're interested but don't know where to start.

Basic Mechanics of Terminal Ballistics



Contents
Introduction
Wound Concept
Incapacitation
Mechanisms of Tissue Damage
My Conclusion
Further Reading


Introduction-
There are some widely circulated beliefs about the effects of high speed projectiles on the human body. Some of these are true and some of them are misconceptions, not founded in the Laws of Physics but in preconceived notions and concepts circulated by popular media such as videogames and movies. This thread is an attempt to provide a source for clarification of the mechanics and factors of terminal ballistics and prevent myself from derailing any more threads. I do not claim to be a professional and of course my word is not law or fact. However I am a physics major and have been studying terminal ballistics and human anatomy and medicine for four years; this doesn't automaticly make me an authority on the subject, but it does carry a bit more credibility than media outlets designed for entertainment, note that this includes the Military channel and History channel. While comments of most any kind are completely welcome, keep in mind that if you're going to tell me I'm flat out wrong, you're going to need to supply some decent evidence, as everything in this article is based upon years of research. Though I will gladly change the article if it is established that I have misrepresented something or provided incorrect information.

Wound Concept-
Standard kinetic energy projectiles such as standard Full Metal Jacket bullets cause harm to a human by destroying organic tissue, damaged tissue may fail to perform its intended task and destroyed tissue certainly doesn't do its job. This can be observed as multiple effects. Destroyed/damaged vascular tissue cannot hold blood and thus may cause harm through loss of blood volume and pressure. Destroyed/damaged neural tissue will not transmit the electrical signals of communication through the body. Destroyed/damaged muscular tissue poses a similar problem as it may not be able to exert and support force required for movement. Destroyed/damaged bone tissue can cause many problems including destruction of local tissue, loss of structural support, and cause of internal poisoning and Acute Stress Reaction, which can lead to circulatory shock. Destroyed/damaged respiratory tissue may result in loss of lung capacity, causing breathing issues, which may result in circulatory shock or even asphyxiation. Destruction of various organ structures can cause severe problems ranging from internal poisoning to severe internal bleeding.

Incapacitation-
Incapacitation can result from:
Loss of consciousness, physical incapability to continue(hereby referred to as "physical incapacitation"), loss of drive to continue (known as psychological incapacitation), or death.
Loss of consciousness can be caused by circulatory shock, asphyxiation, neurological trauma, and poisoning. Loss of consciousness may be short lived, but most people won't be fit to continue an offense after regaining consciousness.
Physical incapacitation is caused when the body is damaged to the point that persisting in given activity is rendered physically impossible due to damage to muscular and bone tissue, or damage to neurological tissue, causing paralysis in relevant locations.
Psychological incapacitation is difficult to pin down, there are far too many factors to predict it or determine its exact causes. Psychological incapacitation may mean the person in question just gave up, maybe he/she intentionally stopped his/her activity to make top priority of seeking medical attention, or maybe he/she just can't focus past the wound he/she has received. There are nearly infinite variables and they tend to be based on the mental state of the person in question.
Death or Brain Death can result from catastrophic destruction of vital structures such as the brain, effectively deleting the victim's being from existence, or it can simply result from severe blood loss and organ failure. This one's pretty intuitive.

Mechanisms of Tissue damage-

I. Mechanical crushing/Stretching of Tissue
This is simple, when a bullet strikes tissue at relatively high velocity, it pushes on the tissue, exerting energy into the tissue, causing it to stretch. As would be found in most any firearm projectile, sufficient projectile energy allows the projectile to continue to stretch the tissue until its elastic threshold has been passed, causing the tissue to tear to relieve tension; as the tissue tears, the projectile is granted access to the tissue beyond the torn tissue, the precess continues as the projectile penetrates and the projectile is gradually ridden of it's kinetic energy, causing it to slow down, eventually to a stop, though many projectiles will penetrate completely through a human without running out of energy. This is the most basic concept of projectile damage; what tissue the bullet hits is damaged/destroyed.

II. Energy Transfer(Temporary Cavity)
When a bullet passes through a fluid medium (organic tissue) it faces fluid drag. Fluid drag causes kinetic energy to transfer to surrounding tissue, by nature this means that the surrounding tissue is "Pushed" away from the bullet radially, this is referred to as temporary cavity and can be observed as temporarily displaced tissue surrounding the path of the bullet.

This can be observed in great quantity on this channel https://www.youtube.com/user/BrassFetcher

*** I cannot stress this enough. This is NOT hydrostatic shock. ***

This phenomenon stretches tissue surrounding the bullet and not just that directly in front of the bullet. This is based on how much energy the bullet transfers to the tissue, temporary cavity is often harmless and leaves flesh mostly unharmed, maybe slightly bruised. Another thing to consider is that a bullet traveling point first through tissue doesn't transfer much energy, no matter how fast it's traveling. If a bullet upsets(yaws, expands, fragments, deforms etc) fluid drag acting on the bullet is greatly increased, causing a significant local transfer of kinetic energy, which may potentially overcome the elastic threshold of the surrounding tissue and cause radial tears. In a study performed by the author of the channel linked above (who is a qualified professional) it was found that, upon upsetting, projectiles with roughly 550 Joules of impact force can cause peripheral tissue disruption, with the effects increasing in intensity with increased impact force. Of course different types of tissue have different thresholds, for more information on this you should read the original article. It should also be noted this is not a property highly valued in military and law enforcement applications and is usually overlooked for other qualities. The most obvious case in which this effect presents itself is in the effects of Anti-Materiele projectiles on living creatures. Otherwise it's not vastly significant, but could be something to keep in mind.

III. Bow Shockwave
This is something that is debated heavily in the scientific community and it would be arrogant for me or anyone else not involved with the scientific community to claim they know better than all those scientists having a world war over the issue. I can simply make observations about the concept. This can be observed in COM shots taken with high velocity (>2000fps) ammunition. It has been observed that people and animals can sometimes faint immediately upon impact of the projectile. This is theorized to be caused by high pressure shockwaves compressing neural components located in the upper torso, causing temporary respiratory paralysis/coma. It should be noted that this could also be explained by local energy transfer to the upper spinal column, which will have similar, or far more serious effects. The concept is widely associated with light, fast projectiles like .220 swift. This actually makes some sense; the faster a projectile attempts to travel through a meduim, the more energy is required to overcome the fluid drag. I can imagine a light (2-4g) projectile hitting a medium with such speed that it slows to a halt almost immediately, transferring most all of it's energy to a small portion of tissue, causing dramatic radial displacement, damaging tissue. Although this would fall under the catagory of Energy Transfer. While this is something that has some merrit, it seems to be inconsistent. Something that urks me about the idea of the shockwave is that I feel people speak of shockwaves without understanding the mechanics of a shockwave. As a shockwave travels through a medium, kinetic energy simply compresses the medium in waves similar to the operation of peristalsis. The only possible damage the shockwave could cause would just be by the movement of one sample of the medium seperate from another, and shockwaves don't cause significant movement on such a small scale. Another thing that I personally question about the concept is that it does not scale proportionally with velocity, despite being linked to velocity; this can be observed in failed incapacitaion from anti-Materiele projectiles such as .50 BMG, and .408 Cheyenne tactical, whose muzzle velocity far exceeds those of most other rounds included in the 'high velocity' group. These failures to incapacitate result from the projectile failing to upset within tissue; this seems to point to energy transfer as the mechanism of action for these rounds. It should also be noted that even shockwaves are a result of energy transfer; so if little energy is transfered, the laws of thermodynamics say that no notable shockwave would be produced. Another far more well known example is failure of 5.56 projectiles to incapacitate at close range (this also happens at long range but that is a different subject). They are reported to go straight through the enemy combatants leaving a very small wound, requiring more rounds on target to stop the enemy combatant. At such close range, the 5.56 round is traveling at a velocity of nearly or over 3000 fps, easily more than enough to be considered high velocity. If it were the velocity causing such deadly shockwaves, then the 5.56 round would be extremely effective at close range with a higher muzzle velocity than that of most full power rifle rounds. These are just some points to keep in mind.

IV. Ballistic Pressure Wave (Hydrostatic Shock)
Same applies here about this being debated.
Remember, this is not the big bubble you see in ballistic gel tests. Hydrostatic shock is the theory that high velocity projectiles can cause remote wounding effects. This is difficult to explain exactly. The concept is that a high velocity projectile traveling through a medium displaces that medium at the velocity with which the projectile travels. For a supersonic projectile, this means that the medium is displaced faster than the speed of sound, this causes what qualifies as a sound wave to propagate through the medium, this wave can cause damage to neural components through pressure. As I've looked deeper into this, I've found that I don't so much have a problem with it. Michael Courtney, somewhat of an authority on the matter, has said that this is, in fact, related to energy transfer. I believe he also said somewhere that the damage can be compared to a serious concussion. So it's no magical heart-exploding shockwave, just a mechanism which can decrease the time to incapacitation. You may hear people blow the effects out of proportion; the effects are there, they just aren't as extreme as people make them out to be.


My conclusion-
I follow these findings to their logical conclusions. The conclusion is that guns don't knock people down like they do on TV. These findings may contradict what you believe about terminal ballistics, but keep in mind, there is much misinformation spread around, it is spread around by videogames and stereotypes and people with a flawed view of the physical properties of the universe. People make terminal ballistics out to be something it's not; people make up new mechanisms of action when they can't explain something. Again, feel free to express distrust in this article, but please do so with logical reasoning and not because stereotypes tell you that loud guns always kill in one shot and that a rifle is more lethal than a handgun just because it is.
Liberate your mind :)

Further Reading-
These aren't exactly my sources, remember that I've been at this awhile, what I've found is from years and many many different websites and books; these are just a few websites and I couldn't find some of the really good ones.

http://www.brassfetcher.com/Wounding Theory/Velocity of Radial Expansion.pdf

http://www.firearmstactical.com/hwfe.htm

http://www.firearmstactical.com/pdf/sanow.pdf

http://www.firearmstactical.com/tacticalbriefs/volume4/number2/article421.htm

http://africanxmag.com/debunking_ballastic_myths.htm

http://www.chuckhawks.com/beginners_stopping_power.htm

http://www.rathcoombe.net/sci-tech/ballistics/wounding.html

http://arxiv.org/ftp/arxiv/papers/0803/0803.3051.pdf
 
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Floyd

FNG / Fresh Meat
Feb 19, 2006
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Waterproof
www.ro50pc.net
Just a few quick thoughts.....nothing earth shattering. I'm guilty of a 'quick read' of your post.


As a hunter, we are always looking for that ideal cartridge and load that will reach our target and expel all of its energy within the target. I.e. energy is wasted once the bullet leaves its target, we 'want' the bullet to stop just before exiting the target. (I always think of that as terminal velocity...lol) But I digress...


Is there any taking into account what happens when the bullet hits solid matter, like a bone. For example, what is the effect of say (arbitrary calibers pulled out of thin air) a 115grain 9mm pistol bullet shot from a pistol at (arbitrary distance, also pulled from thin air) 50m vs a 150 grain .30-.06 rifle bullet (same distance) when it hits:
a) the thigh bone
and/or
b) the sternum. (other than both will hurt like hell)


In war we generally deal with FMJ projectiles and not hollow point or partition bullets, so we won't go there (though I notice that many of the articles cited do mention them as it pertains to 'stopping power'). But it leads to my next question, as it is vaguely related.. ;) Is there any measureable difference in effect upon tissue and cavity from the shape of the bullet? I'm thinking in terms of the rather rounded style of (oh say) a .45 cal bullet vs the sleek design of a boat tail spritzer bullet? Same velocity, same caliber. (so many variables in ballistics....)
 
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mrsirr

FNG / Fresh Meat
Apr 12, 2013
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Over here, no not there, here.
Is there any taking into account what happens when the bullet hits solid matter, like a bone. For example, what is the effect of say (arbitrary calibers pulled out of thin air) a 115grain 9mm pistol bullet shot from a pistol at (arbitrary distance, also pulled from thin air) 50m vs a 150 grain .30-.06 rifle bullet (same distance) when it hits:
a) the thigh bone
and/or
b) the sternum. (other than both will hurt like hell)
Yeah bone can be kinda tricky, but sometimes not. It partially depends on how much resistance the bone presents. I think the vast majority of bullets will break through the sternum. The thigh bone is really big and thick so it can stop some bullets; in this case I think both rounds would break the thigh bone. Of course at every point that the bone breaks, energy from the bullet transfers and is released, so the bullet will be slowed down and the impact will usually destabilize the projectile. A good example of this is that, when striking a limb, .50 BMG may just pass straight through; but if it were to stirke a bone of sufficient resistance, it could draw enough of the bullet's energy and destabilize it enough that a significant portion of it's energy could be transfered, and for a round like that, it usually means you're going to lose that limb.
In war we generally deal with FMJ projectiles and not hollow point or partition bullets, so we won't go there (though I notice that many of the articles cited do mention them as it pertains to 'stopping power'). But it leads to my next question, as it is vaguely related.. ;) Is there any measureable difference in effect upon tissue and cavity from the shape of the bullet? I'm thinking in terms of the rather rounded style of (oh say) a .45 cal bullet vs the sleek design of a boat tail spritzer bullet? Same velocity, same caliber. (so many variables in ballistics....)
There is technically a difference in energy loss for different shapes. A less hydrodynamic bullet (round nose .45) will transfer more of it's energy as it penetrates due to its inefficient shape. This means it would proportionately make a larger temporary cavity when penetrating on a linear path. However, given that most spitzer rounds are used by more powerful rounds, there's more energy there anyway. Of course the final nail in the coffin is that neither will make very much temporary cavity unless they upset. So the answer is that there isn't really a notable difference.
Although a pointy bullet traveling at lower velocities is more likely to make a permanent cavity with the diameter of the very tip of the bullet instead of the widest point, since tissue is elastic.

Anybody else can chime in or whatevs.
 

Tomcat_ha

FNG / Fresh Meat
Nov 21, 2005
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regarding hydrostatic shock. Can that actually also be related to physical weaknesses in the people shot? Like in the case of the brain hemorrhage having unusually weak blood vessels or even clogged arteries?

Also regarding shape of bullets ive read somewhere sometime that german 7.62 nato rounds are different from the american ones in shape and thus they fragment heavily when they enter the body causing much more damage.
 

mrsirr

FNG / Fresh Meat
Apr 12, 2013
4,077
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Over here, no not there, here.
Yeah I'd imagine that internal hemmoraging thing could vary. Alot of factors can't be predicted because they're always different. And yeah, the German 7.62 round has a thinner jacket, I think it's a cupronickel plated steel jacket and it is a lot more likely to fragment in tissue because of that.