Stinky:
As you said, you opened a can of worms. I am not questioning your understanding of physics, etc., but have pondered this same question many times.
I have heard the shockwave theory many times before, and though it is supported from the standpoint of physics relative to inanimate objects such as Russian tanks, it is not a relevant theory for objects of flesh, such as elk, deer, or in the case of military studies done on such, humans.
A friend who has done studies for the military on such things tells me that shockwave theory as it relates to tissue damange, is invalid. He explains that killing power on animals is related to the wound channel and the amount of tearing or destruction on non-pliable tissue. Also is the compression and compaction of the areas hit and the ability of those organs, bones, etc to withstand compression and compaction.
Here is an article that focuses on similar topics.
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Introduction
Terminal ballistics is the study of the interaction between penetrating projectiles and body tissues. Evolving in tandem with small arms development, most of our current understanding of terminal ballistics has come from the hard work of dedicated trauma surgeons, starting with Dr. Emile T. Kocher's groundbreaking work towards the end of the 18th century up to contemporary times with Dr. Martin L Fackler. Unfortunately, much of their work is relatively difficult if not impossible for the general public to access.
For the most part, the science of wound ballistics has focused on military small arms ammunition (ie: centerfire rifle ammunition in common military calibers such as 5.56 NATO, 7.62 NATO) and pistol ammunition (such as the ubiquitous 9mm, .40S&W, and .45ACP). Shotgun wound ballistics seem to have been somewhat neglected in the available literature; somthing that is regrettable and as a result a general lack of knowledge surrounds both the effectiveness and limitations of the shotgun in armed conflict. Our intent with this section is to somewhat fill that gap. Our hope is that this will arm you with some basic information that will enhance your capability to make informed choices with respect to shotgun ammunition selection and application in a tactical situation.
Wounding Mechanisms
Penetrating projectiles cause injury from two wounding phenomenon; crushing and stretching. As the projectile passes through tissue, it crushes tissue creating what is known as the permanent cavity. The diameter of the cavity is, for the most part, in proportion to the presenting area of the projectile although this will vary depending on the profile of the projectile. Blunt, flat nosed projectiles will crush a wider permanent cavity as compared to one of a more aerodynamic shape (ie: a long and gently tapered high velocity rifle bullet). Within the world of shotgun ammunition there are typically very limited geometries to consider, as most shot is round and most slugs have a fairly blunt profile.
The second type of damage a projectile passing through tissue can cause results from the walls of the permanent cavity being stretched radially outwards. The degree to which the tissue is pushed laterally is described as the temporary cavity and all damage caused is a result of this stretching. The degree of damage caused is typically a function of the elasticity of the tissue, and the various tissues of the body will behave differently in this regard. For example, muscle tissue is relatively elastic and as such not terribly prone to significant stretching damage whereas more inelastic tissues such as the liver wound sustain considerable damage from stretching of equal magnitude as what we inflicted on the muscle group.
What is most important to recognize with medium/low velocity projectiles typical of most shotgun loads is that their primary wound creation mechanism is the permanent crush cavity caused by the passage of the projectile. Damage caused by the temporary stretching by displaced tissue is not a reliable wounding mechanism and as such little attention should be paid to the temporary stretch cavities illustrated in our ballistic gelatin testing. To re-quote material we talk about in our article on shotgun ammunition, Dr. Martin Falker writes:
"A large slow projectile will crush a large amount of tissue, whereas a small fast missile with the same kinetic energy will stretch more tissue but crush less. If the tissue crushed includes the wall of a large blood vessel, far more damaging consequences are likely to result than if this vessel absorbs the same amount of energy in being stretched or temporarily displaced by cavitation."
Myths
Regrettably there are many myths that have recently wormed their way into the popular literature relating to how projectiles wound. Likely the most popular of these are the various incantations of "shock wave" dogma. Sometimes correlated to the temporary stretch cavity observed in gelatin testing, the premise of this theory is that hydraulic shock effected by the passage of the projectile through tissue sets up a wave that can travel through the body, damaging organs and tissues distant to the wound tract. The simple truth is that there is no scientific evidence to suggest this phenomenon actually occurs.
Another variation of the "shock wave" theory contends that the body's nervous system can easily be "overloaded" by the energy absorbsion. While there are some documented cases of people collapsing without any apparant damage to their central nervous system, these have typically all happened with high power rifle ammunition where the bullet has passed very close to the spinal column. It is not an easily repeatable phenomenon and even less likely to occur with pistol and shotgun ammunition. As such it is not a reliable means of incapacitation and further study is likely required.
Ordinance Gelatin Testing
When Dr. Martin Fackler of the Letterman Army Institute of Research developed what are now the standardized gelatin testing protocols it was with the intent of being able to better simulate gunshot wounds in the human animal. The primary objective of this ballistic testing methodology created by Dr. Fackler was a standard of reference for use in the comparison and evaluation of varied surgical corrections and treatments.
The preparation of ordinance gelatin is typically held to a very specific procedure. Once the gelatin has been prepared, it is then calibrated immediately before use to demonstrate that it falls within a relatively narrow window of physical properties designed for block to block consistency. This calibration process is important for wound ballistic researchers as it sets a standard by which observations from one gelatin block can be meaningfully compared to those observed in another block. The calibration standard is typically 8.5cm of penetration by a steel BB with an initial velocity of 590fps.
If the penetration of the steel BB at 590fps does not meet the calibration standard, all is not lost though as excellent data collected by Duncan MacPherson allows correlation and correction provided the velocity and mass of the BB fall within the calibration protocol. tacticalworks.ca gelatin testing has all been done in accordance with calibration and correction standards established by both Dr. Fackler and Mr. MacPherson.
***IMPORTANT INFO***
The reader must be advised that ballistic gelatin testing does not, and cannot reliably predict the incapacitation potential or "stopping power" effected by the various ammunition.
Properly prepared ordinance gelatin used as a testing media simply approximates projectile wound profiles as observed in adult swine leg muscle tissue; it does not describe exactly how any projectile may behave in all conditions. Interpretation of the wound profiles must be limited to simple comparison of the two different tissue disruption mechanisms.
Far more relevant than the evaluation of one type of ammunition as compared to another is the weapon operator. There are absolutely no substitutes for quality training, effective & frequent practice, well developed tactics, and a high level of fitness.
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So, this supports the theories as to why controlled expansion bullets are so popular and effective. They are ballistically superior to blunt nosed bullet. And, upon entry, they expand larger than original diameter, creating large wound channels that do a lot of tearing, compression, compaction, and damage.
Which is why bullet placement is so important. As my friend who has consulted with the military on this topic stated when I seemed to still cling to the shockwave theory - If shockwave theory was what killed animals, shoot every elk in the a$$ and make sure they absorb all the energy, as the shockwave theory will be fully enforced upon the elk. Will he drop like hit by lightning? Nope.
Bullet placement is so important because of the the mechanics of wounding that cause death - tearing, compression, compaction, etc. We are placing bullets in areas that have the greatest damage based on these principles of wounding.
After talks with this person, I am now convinced that bullet placement is item of importance #1-10, proper caliber for game selected is #11, and bullet construction is item #12, with all the other theories/principles being much further down the list.
The theory that an exited bullet is wasted energy is somewhat true, but not necessarily important.
Example: A .270 doesn't exit, and all energy is absorbed. Good. A .300 has 145% of the energy that the .270 has and provides an exit wound by utilizing all but 15% of its energy. So, would you rather have all the energy absorbed from the .270, or 30% more absorbed by using a .300, and getting an exit wound?
This is merely an example to prove that an exit wound is not necessarily a bad thing. It is in no way my statement that a .270 is incapable of killing an elk.
This topic can be argued to the end of time, but most scientific studies of the shockwave theories used for military ordiance and damage to armor, are not considered valid for studies related to lethality of bullets in animals.
Given the many opinions on this topic, I offer mine and will rest with that.
I have many good elk rifles from the .270 to .300 and with proper placement of good bullets, they are all more than lethal on elk.
Happy Hunting!
"Hunt when you can - You're gonna' run out of health before you run out of money!"