Shotgun Terminal Ballistics

 

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."

The key in selecting effective wounding ammunition for deployment in a tactical shotgun is to balance the desire for multiple projectiles (higher first round hit probability) with each projectile's inherent capability to effectively wound. Hopefully our gelatin tests listed lower provide you with a bit more information to effectively evaluate the myriad of ammunition available as it relates to your own requirements.  

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 we have tested here at tacticalworks.ca.

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.

***END IMPORTANT***
 
 

Calibrated Wound Profile Library

 

Hunting Data

One thing we've long felt has been missing from much of the available literature is decent real-world examples detailing actual shootings. While grim in nature and certainly not the controlled conditions of a laboratory environment, there is still much of value to be gleaned from this type of documentation. To circumvent the ethical issues surrounding making public information on shotgun shootings involving people (albeit likely opening the floodgates to a parallel form of ethical controversy), we've instead elected to use examples gathered from a hunting environment where prey animals approximating the physiological size and makeup of Homo-sapiens were shot with shotgun ammunition.

 

Body Armour Discussion

Most ballistic body armour is capable of stopping shotgun ammunition from penetrating through the armour and into the tissue of it's wearer. As such, it is commonly thought that body armour successfully defeats 12 gauge ammunition; this thinking is significantly flawed. The flaw lies in the belief that defeating a projectile via body armour is a sole function of preventing the projectile from penetrating. What can makes the flaw so potentially fatal is the physiologically catastrophic blunt trauma the energy of a typical shotgun round is capable of generating.

If you recall from our ammunition and wound ballistics discussions, most of the modern wound ballistics experts believe that consideration of kinetic energy when attempting to build an understanding gunshot wounds is grossly misleading. Having an understanding of kinetic energy is critical when it comes to exploring blunt trauma through body armour. The higher the kinetic energy applied to a per-unit surface area of the vest, the more likely it is that crippling blunt trauma is inflicted.  

Body Armour Examples