Formulating the Pressure Wave Hypothesis

[MCgunner]

We had hunting experiences similar to yours which helped lay the groundwork for the formulation of the pressure wave hypothesis. Together with the peer-reviewed research referenced in the initial post of this thread, we though we had a hypothesis worth more careful testing.

The trouble at this point was the lack of published data that inspired confidence. The anonymity of the Strasbourg tests and negative views of the M&S data set gave us pause. Consequently, we designed the deer experiment to test the hypothesis that Strasbourg was a wholesale fraud, and we found a 90% confidence level that the Strasbourg average incapacitation times are reliable.

We also gave careful consideration to the criticisms of the M&S data set and we concluded that many of the criticisms are exaggerated, and where there are some valid criticisms, these impact only the accuracy of interpreting the OSS rating as a relative measure of bullet effectiveness. Together with the fact that the OSS ratings are highly correlated with the Strasbourg test average incapacitation times (which we experimentally showed are not fraudulent), we had enough confidence to develop a model with the M&S OSS data set.

It is notable that both the Strasbourg authors and Marshall and Sanow were suggesting a pressure wave mechanism 14 years ago, and in the time since then, the field of neurology has shown that a pressure wave applied directly to the brain can cause both incapacitation and neural injury. All we've done is connect the dots.

Well, I don't really know what motivates Dr. Fackler's research, but I know that some of the lesser intellects in the gun world have a definite agenda to discredit what they see as the opposition to their great holy grail, the 230 grain .45 caliber bullet at 800 fps. If JMB had designed the 1911 to accept the 9x19, they'd be trying to discredit Fackler. There are agendas in the gun media and the gun world and you can see that right here on this board. Thus, the never ending debate, stupid articles on BOTH sides about the subject from gun writers with journalism degrees and guys that have been in combat a couple of times and know it all about fighting calibers. They go so far as to suggest that rifle calibers don't count, somehow don't relate to handguns. The rifle bullet is somehow ruled by different physics, the realm of quantum physics, ultra high speed particles, that nobody understands, or something.

I suspect a lot of folks that claim the .45 as the end all and that Chuck Taylor got it right because their 9mm won't blow the pins down like their .45, have never shot an animal and cleaned it afterwards. I own a .45ACP and like it a lot, but I know there's more to a bullet's incapacitation potential than its diameter.

Thank you for posting this thread. It has been a very interesting read.

 

[lbmii]

What was the deer experiment?

 

[Michael Courtney]

"The deer experiment" supports the veracity of the Strasbourg goat tests by using a similar experimental design observing incapacitation of whitetail deer by carefully controlled shot placement in the center of the chest. Predictions based directly on the Strasbourg tests were validated in whitetail deer by showing that bullets of comparable wound channel volumes incapacitate much more quickly when a large ballistic pressure wave is present. Using comparable shot placement as the Strasbourg tests, one obtains an accurate prediction for the average incapacitation distance of deer by multiplying the Strasbourg average incapacitation time by the average death run speed of deer, 10 yards per second. This supports the Strasbourg results that reported a large pressure wave causing rapid incapacitation. (The Strasbourg tests used a high-speed pressure gauge inserted into the carotid artery.) Upon necropsy of the deer, we observe tissue damage due to the pressure wave for some bullets. This damage was remote from the wound channel and well beyond the range of the temporary stretch cavity.

Here's a preliminary summary for two loads:

Load: .357 Sig 115 grain Triton Quik-Shok at 1450 FPS
Mean Incapacitation Distance: 49.6 Yards
Uncertainty in Mean Incapacitation Distance: 14.6 Yards
Predicted Incapacitation Distance (from Strasbourg tests): 48 Yards
Permanent Crush Cavity Volume: 4.1 cubic inches
Pressure Wave Magnitude (on surface of 1" diameter cylinder centered at wound channel): 986.8 PSI

Load: 9mm 147 Grain Winchester JHP (WWB) at 990 FPS impact velocity
Mean Incapacitation Distance: 97.6 Yards
Uncertainty in Mean Incapacitation Distance: 15.7 Yards
Predicted Incapacitation Distance (from Strasbourg tests): 99 Yards
Permanent Crush Cavity Volume: 4.2 cubic inches
Pressure Wave Magnitude (on surface of 1" diameter cylinder centered at wound channel): 305.6 PSI

These predicted incapacitation distances simply take the most comparable load used in the Strasbourg goat tests and multiply the Strasbourg incapacitation times by 10 yards per second. (This relation between average velocity and incapacition time in deer is from previously published work testing hunting bullet effectiveness in deer.) Using Chi-square analysis, one can use compare the predictions from Strasbourg with our results and conclude with at least 90% confidence level that the Strasbourg results are not fraudulent.

Because the PCC volumes between the two bullets are comparable and the incapacitation distance for the 115 grain Quik-Shok is significantly smaller, one can conclude with at least 90% certainty that there is a significant contribution to incapacitation other than the PCC volume.

With 90% confidence that the Strasbourg average incapacitation times are genuine, one can use regression analysis (least squares fitting) to show correlations between the Strasbourg average incapacitation times and gelatin parameters (PCC, TSC, pressure wave). Depending on the model, one obtains correlation coefficients are between R=0.6 and R=0.7 for TSC alone. These are significantly larger than correlations between the average incapacitation times and PCC alone (R < 0.55). The pressure wave magnitude gives the highest correlation coefficient (R=0.85) in regression analysis using a single independent variable. A model using both pressure wave and PCC does a bit better at giving the incapacitation times (R > 0.9).

In our study on deer, the animals were weighed and necropsied to minimize confounding effects. Sample groups for different loads have nearly the same average weight and weight distributions. Shot placement was confirmed by noting the entry and exit points in the thoracic cavity. All bullets entered between the 4th and 10th ribs (counting from the back) and within 1" of the horizontal mid line. All deer were hit within 15 degrees of being squarely broadside. Deer that were determined to be injured or in poor health prior to the shot were excluded. All deer were shot within 3 yards of the same range and in the same level terrain in an area of moderately thick vegetation that does not impede the movement of deer.

Michael Courtney

 

[MCgunner]

So, I'm picturing some lucky &#(%&#@ graduate student getting to hunt the triple 7 ranch for the advancement of science and writing his graduate thesis on it to boot! That's green with envy. Beats the heck out of population studies of Penaeus aztecus in the Galveston Bay complex, eh?

However, sounds like it was a little more controlled than an actual hunt. Probably make the PITA type's skin crawl. Likely that's the reason the Strasbourg testers are anonymous.

 

[pest3125]

Hi Michael,
Just out of curiosity, what was the title of your PhD thesis at MIT?

 

[ghost squire]

You don't find it even remotely interesting????

I do, I'm just saying... as is Michael Courtney, that it should be taken within context, there is no magic bullet.

Everyone knows (including Fackler) that there are other mechanisms to wounding then permanent crush cavity. But when you're talking about standard powered handguns (you know, the ones with flash that doesn't blind you and recoil that stings your palms) its the only thing you can really rely on IMO. There is a lot of talk here comparing handgun to rifles, which makes me nervous. For the most part they are totally different.

I have a request. Would anyone care to do a test with service caliber handguns comparing the volume of cardiac muscle tissue destroyed by whatever means after passing through the FBI standard of a tee-shirt, a flannel shirt and a denim covered down jacket at 20 yards? A tall order I know, but I think just about everyone would consider this the ultimate test of handgun cartridge effectiveness. Perhaps the only modification I would make to the FBI standard is the addition of a homogenous sheet of something very closely resembling the sternum (in terms of it affecting the bullet), in front of the heart, and between those maybe an inch or two of clay.

When you think about it it isn't unreasonable that this shot would be encountered. A large part of North America sees very cold weather during part of the year, and a frontal shot through the sternum and into the heart is the one most likely to be encountered. I'll admit that 20 yards is out there when it comes to defensive handgun encounters, but wouldn't you like to know the cartridge you use is "up to it"?

 

[MCgunner]

I'm pretty well confident that the major calibers can shoot through a coat. I mean, I've never had a .357 stop in a deer's thorax, even when breaking through a clavicle, much less a coat. And, deer have deer skin coats built in! The construction of the bullet is most important here. If you want over-penetration in a .45 or a .9mm, you can get it just fine and get some amount of energy transfer by using a flat point lead bullet. I'll still be loading mine with hollow points, though. I'm running around here mid winter in a T shirt. In south Texas, 50 degrees is considered COLD! Ain't like we gotta wear mukluks. In fact, afternoon, I've had the AC running for the last couple of days.

I totally agree that it's it's all academic. I mean, it's not going to change the world to discuss or know anything about the subject. But, I enjoy reading about it. I have already made up my mind on carry guns at this point. I'm thinking about another one, but hey, I ain't sellin' what works for me now! Hopefully, I'll never have to test the terminal effectiveness of any of 'em except on game animals. I fully intend to keep "testing" 'em on game animals.

Who seem to pay more attention to this sort of study are people such as FBI and various police departments who purchase duty guns for their departments. As an individual, I am only interested in it as an academic thing, just because....

 

[MrAcheson]

One might think that someone suggesting that a Physicist "doesn't seem to have and adaquate understanding of wave propogation phenomenon" would know how to spell the word, "propagation" and also know to use the plural "phenomena" because there are lots of waves which do lots of things.

Yes my grammar and spelling stink. As if typos on an internet message board matter. Did you understand what I was saying? Yes.

I agree that the terminology used in current literature is poor from the point of view of physics or engineering. A great example of this is the aforementioned "hydrostatic shock". But what do you expect from articles often written by MDs (like Fackler) who probably haven't had physics since the freshmen year of their undergraduacy? If my work in biomedical engineering taught me anything, it was that medical doctors don't do equations or math unless it involves calculating a pharmaceutical dosage.

However, I don't think you are attacking their argument. Instead you are attacking some sort of caricature of their argument based on their flawed terminology. For instance several of your criticisms of Fackler hinge on his use of the term "sonic". Is he actually restricting his analyses to pressure waves of sonic frequency or is he simply applying an poor technical description (from my perspective) to his own work?

Also most of my experience with damage through pressure wave effects (like hydrodynamic ram) show that the vast majority of damage from a pressure wave is derived from the initial overpressure and impulse which is of very short duration. Once the projectile fully enters the medium (in this case a fluid tank), the actual overpressure drops precipitously and you enter a new phase characterized by cavity formation. Now I'm talking about a phenomenon occuring in a newtonian fluid, not human body tissues which are very non-newtonian, but some of the theory is certainly applicable. In my experience, Fackler's assessment of pressure wave then temporary cavity is not unusual or even considered particularly controversial.

 

[Michael Courtney]

A great example of this is the aforementioned "hydrostatic shock". But what do you expect from articles often written by MDs (like Fackler) who probably haven't had physics since the freshmen year of their undergraduacy? If my work in biomedical engineering taught me anything, it was that medical doctors don't do equations or math unless it involves calculating a pharmaceutical dosage.

You noticed that too.

However, I don't think you are attacking their argument. Instead you are attacking some sort of caricature of their argument based on their flawed terminology. For instance several of your criticisms of Fackler hinge on his use of the term "sonic". Is he actually restricting his analyses to pressure waves of sonic frequency or is he simply applying an poor technical description (from my perspective) to his own work?

Actually, I don't think Fackler has actually published any of his own research showing anything at all about the ballistic pressure wave ("sonic" or otherwise). He references a paper by Harvey et. al., makes some vague comments about not seeing any effects in his experiments (that aren't designed to see pressure wave effects), and references a private communication about Vietnam era trauma surgeons not seeing broken bones or blood vessels resulting from a pressure wave.

So while you might be right that I shouldn't make a point about Fackler's imprecise language, in his zeal to denounce the valid research of Sunseon et al, Fackler strains the bounds of credulity in areas where a medical doctor really should know better.

Fackler writes:

A review of 1400 rifle wounds from Vietnam (wound Data and Munitions Effectiveness Team) should lay to rest the myth of “distant” injuries. In that study, there were no cases of bones being broken, or major vessels torn, that were not hit by the penetrating bullet.

How can a medical doctor refute modern observations (using new methods) of microscopic damage to nerve cells by referring to the absence of observations of broken bones or torn blood vessels in a Vietnam-era observations from trauma surgeons? The Vietnam-era study was not looking for distant nerve damage, and they did not employ the methods used by Suneson et al.

Also most of my experience with damage through pressure wave effects (like hydrodynamic ram) show that the vast majority of damage from a pressure wave is derived from the initial overpressure and impulse which is of very short duration. Once the projectile fully enters the medium (in this case a fluid tank), the actual overpressure drops precipitously and you enter a new phase characterized by cavity formation. Now I'm talking about a phenomenon occuring in a newtonian fluid, not human body tissues which are very non-newtonian, but some of the theory is certainly applicable.

Look up some of the journal articles I've referenced, as well as some of the articles on the fluid percussion model of traumatic brain injury.

There is also a study in rabbits showing that TBI can result from underpressure.

In my experience, Fackler's assessment of pressure wave then temporary cavity is not unusual or even considered particularly controversial.

That doesn't mean it is correct. The leading edge of the pressure wave propagates at the speed of sound in the medium. But concluding that's all there is to the ballistic pressure wave would be like concluding that an earthquake is over after the P wave has passed.

Think about Doc Edgerton's photographs of a bullet passing through an apple. First, the bullet passes through the apple, and the photograph shows the apple with two bullet holes and the bullet a few inches past the apple. Since the bullet has exited the apple, it is clear that the leading edge of the pressure wave (sonic velocity) has reached the surface of the apple, but the apple remains whole until a later component of the pressure wave causes the apple to explode. (Do a web search on "How to Make Applesauce at MIT."


Putting a high-speed pressure gauge into ballistic gelatin demonstrates that there is a lot more to the ballistic pressure wave than the compression waves that travel the speed of sound. Putting the ballistic gelatin into something to simulate a rib cage and skin demonstrates even more longer-duration activity of the ballistic pressure wave.

Some of the references cited in the initial post actually insert a high-speed pressure gauge into the living test subject. Now, these guys think like biologists, so they get thrown a bit by the fact that the leading edge of the pressure wave arrives in a time consistent with the speed of sound in water. They may have failed to realize that the duration of the wave indicates either that there are more slowly traveling components to the wave and/or that the wave reverberates around for some time.

Suneson et al. report that the leading edge of the wave travels a distance of roughly 0.5m in about 0.34 milliseconds. Yet the duration of the wave is 1.5 milliseconds. Clearly, there is more to the wave than the leading-edge sonic component.

Our own work indicates that the ballistic pressure wave can have a duration as long as 10 milliseconds for bullets impacting the thoracic cavity. The wave components that arrive first (sonic velocities) have more high-frequency components, and the later arriving wave components are a mixture of high-frequency components (possibly reflections of the leading edge) and lower frequencies.

At this point, it remains an open question whether the leading edge (high-frequency) or later (lower frequency) components play a greater role in incapacitation. This question is worth addressing in later research because one might design bullets to concentrate more energy in the more effective frequency range.

For now, we have shown that incapacitation is well-correlated with the peak pressure magnitude.

Michael Courtney

 

[agtman]

10mm Pressure Wave = Terminal Shock & Awe

Given this discussion, it's seems pretty clear that among the so-called "service calibers" chambered in autoloaders, * only the 10mm AUTO in its high-performance manifestions creates the type of pressure wave capable of nearly instant incapacitation across a range of bullet-weights.

In terms of pressure-wave theory, think of the 10mm as a ballistic tsunami.

On the light-n-fast end of the 10mm's power range, there's Double Tap's 135gn 10mm Nosler HP @ 1600fps/768fpe. Out of a 6" KKM barrel, that same load was chronographed @ 1785fps/955fpe.

On the heavy & fast end, there's DT's 200gn 10mm hardcast BearTooth @ 1300fps/750fpe. BuffaloBore markets a Speer "Unicore" 180gn 10mm HP @ 1350fps/728fpe. Similarly, there's PowerStrike Ammo's 180gn 10mm Gold Dot HP @ 1325fps/702fpe.

An example of a full-throttle "middle-weight" 10mm load is DT's 165gn 10mm Golden Saber HP @ 1425fps/744fpe.

Now contrast any of the above with a standard 9-minimeter load. In comparative pressure-wave language, a 9mm barely creates a ripple at the shallow end of the baby pool.

Heh, heh ...





* By "service calibers," I'm including: 9mm, .357Sig, .40S&W, 10mm, & .45acp.

 

[Michael Courtney]

Given this discussion, it's seems pretty clear that among the so-called "service calibers" chambered in autoloaders, * only the 10mm AUTO in its high-performance manifestions creates the type of pressure wave capable of nearly instant incapacitation across a range of bullet-weights.

The range of penetration depths is more important than the range of bullet weights, and there can be important exceptions to the "conventional wisdom" that heavier bullets penetrate more deeply. Greater bullet weight is no guarantee of more penetration, and some of the lighter bullets also penetrate well. The "conventional wisdom" ceased to be true with the development of bonded designs, solid copper bullets, etc.

In terms of pressure-wave theory, think of the 10mm as a ballistic tsunami.

It's a step up from the .40 S&W, but really more of an incremental improvement than a tidal wave.

Now contrast any of the above with a standard 9-minimeter load. In comparative pressure-wave language, a 9mm barely creates a ripple at the shallow end of the baby pool.

The pressure wave of the better standard pressure 9mm loads is about half the size of the best 10mm loads. This is not insignificant, but not really the difference between a ripple and a tidal wave.

When we want to make a large ballistic pressure wave, we use a 110 grain VMAX loaded to 3400 FPS in a 30-06. This pressure wave is about 3 times larger than the 135 grain load in 10mm, but I still wouldn't consider it to be a tidal wave.

Michael Courtney

 

[agtman]

Doc, thanks for your comments, but my pressure-wave "analogies" were intended more as tongue-in-cheek levity for this thread.

Sorry if they detracted from the academic points being debated here.

 

[thales]

*


Dr. Courtney,
I am interested in precisely how you differentiate between the pressure wave and the temporary cavity as to their relative effectiveness in causing incapacitation. It appears a non-trivial question since the two seem to be highly correlated.


*

 

[McCall911]

I'm an armchair ballistician at best, so I feel as if I'm bringing 2 cents to a million-dollar discussion. But I would like to add just this much, even if they are only questions:

I don't know if I'm talking about the same thing as Michael Courtney, but it's long been my opinion that the importance of the Temporary Cavity effect has been overlooked or ignored in terms of real-world shootings.

Certainly in results from ballistic gelatin shootings, the Temporary Cavity may have secondary importance because the gelatin simply returns from that hyper-extended state of the Temporary Cavity to the smaller Permanent Cavity. But this rushes past one important fact: The force against the gelatin which causes it to form the larger Temporary Cavity to begin with. This is what I am referring to as "the Temporary Cavity effect."

(Sorry to seem morbid, but I do have to get graphic here.)

However, we know that living beings are not composed of ballistic gelatin. We have internal organs whose operation might be disrupted by the Temporary Cavity effect. For instance, a shot near the heart: Could this shot not disrupt the heart, or even stop it, due to the force or pressure exherted against it? Could the Temporary Cavity effect also not be able to disrupt, burst, or sever arteries internally, causing quick incapacitation due to internal hemorrhage? And what about the stomach? Since it is a hollow organ which is vulnerable to damage, might it not also be damaged to the point of incapacitation because of a violent internal force against it?

I'm not asking these questions rhetorically, because forensics is not my field. It's just that I really don't know.

Anyway, I'm reading this discussion with great interest.

Thanks for your contribution, Michael Courtney. Apologies if I've just restated what you have been talking about.

 

[Michael Courtney]

*


Dr. Courtney,
I am interested in precisely how you differentiate between the pressure wave and the temporary cavity as to their relative effectiveness in causing incapacitation. It appears a non-trivial question since the two seem to be highly correlated.


*

The pressure wave magnitude is highly correlated with the temporary cavity volume, so as predictors of incapacitation, the differences are small. However, the pressure wave itself has the potential to effect tissue beyond the physical reach of the temporary cavity. The temporary cavity only has a diameter of 3-4" for most pistol bullets. However, we have detected tissue damage as far as 12" from the bullet impact, and other researchers (using more sophisticated techniques) have detected neural damage as far as 19" from the bullet impact (see references to initial post).

We also believe that the pressure wave rather than the temporary cavity is the stronger causal agent of rapid incapacitation because both our group as well as other research groups have observed incapacitation to result from the application of a pressure wave to live animals without the presence of a temporary cavity.

The final reason we believe the pressure wave is the mechanism is because even though it is highly correlated with temporary cavity volume, models using the pressure wave magnitude and crush cavity are a bit more accurate than models using the temporary cavity volume and crush cavity at describing quantitative measures of incapacitation.

Michael Courtney

 

[benEzra]

(Michael Courtney)
The pressure wave of the better standard pressure 9mm loads is about half the size of the best 10mm loads. This is not insignificant, but not really the difference between a ripple and a tidal wave.

Out of curiosity, how do the 9mm higher-velocity +P and +P+ JHP's compare to the 10mm in terms of the pressure wave magnitude? I know M&S think very highly of, say, the Cor-Bon 115gr +P and various 115-gr and 124-gr +P+ loads.

 

[thales]

We also believe that the pressure wave rather than the temporary cavity is the stronger causal agent of rapid incapacitation because both our group as well as other research groups have observed incapacitation to result from the application of a pressure wave to live animals without the presence of a temporary cavity.

*


Yes, I noticed that you tested the pressure wave without the temporary cavity. Have you tried testing the temporary cavity without the pressure wave? Do you think it advisable and practical, or impractically difficult to separate that way?

I'm just trying to be thorough in understanding this.

Thanks


*

 

[jeepmor]

Pressure waves

Nice work Mr. Courtney, you have placed the measures of science on something that has been obvious to the hunter for quite some time. I recall watching a pig be shot with a hunting rifle that was filmed with a high speed camera. You could see the pressure waves ripple like a stone thrown in water away from the impact site. It was pretty obvious to me, at 12 years old in a hunters safety course, that this was largely contributing to the seemingly instant demise of the animal, not just the bullet passing through it's body. I think they called it hydrostatic shock then. Which I simply interpreted as the energy transfer from the bullet to the medium being penetrated, in this case, a swine's flesh and bone.

Also, recently watching "myth busters" shoot into water to bust a myth. They found that shooting high energy rounds such as the 30-06 and 50 BMG into the water with FMJ bullets, there was so much energy imparted that the bullet disintegrated and never reached it's target of ballistic gelatin some 10 feet or so under the surface of the water. However, the handgun bullets, also FMJ, did penetrate the water quite effectively.

However, I was disappointed that they did not have any underwater high speed cameras in operation to actually observe this occurring.

I possess a BS in Mechanical engineering and would really like to read more of your work. You state your case very well and support it with plenty of data, I just like to see it all in one place, it would be a great technical read on energy transfer mechanics, which is simply what it is. Although, when is physics ever simple.

MIT eh, you're gonna be disappointed with the real world coming from an institution like that. Enjoy your physics study while you can and hope you can get a government job where you can continue pursuing this work. Everywhere else, I suspect, would just want you to design the "magic" bullet for their respective logo. Not to disparage your work or anything, but I found my college work, albeit only at the bachelor's level, to be much more gratifying and exciting than anything I've done for my current employer of 11 years, the worlds largest semiconductor manufacturer.

jeepmor

 

[Michael Courtney]

Out of curiosity, how do the 9mm higher-velocity +P and +P+ JHP's compare to the 10mm in terms of the pressure wave magnitude? I know M&S think very highly of, say, the Cor-Bon 115gr +P and various 115-gr and 124-gr +P+ loads.

For equal penetration depth and percentage of retained bullet mass, pressure wave magnitude is proportional to kinetic energy, so the hottest 10mm loads have nearly an 80% advantage in pressure wave magnitude on the hottest 9mm loads. See my earlier post on the Physics of the Ballistic Pressure Wave for the details.

Michael Courtney

 

[Michael Courtney]

*


Yes, I noticed that you tested the pressure wave without the temporary cavity. Have you tried testing the temporary cavity without the pressure wave? Do you think it advisable and practical, or impractically difficult to separate that way?

*

Getting a temporary cavity without the pressure wave is more difficult to arrange experimentally. We have no plans to attempt this. The best approximation I know of to a temporary cavity with a small pressure wave is a target wearing kevlar, and there is ample anecdotal evidence that this arrangement does not cause incapacitation.

Michael Courtney

 

[thales]

*


If you were to get incapacitation with the pressure wave without the temporary cavity, and get little or no incapacitation with the temporary cavity without the pressure wave, then that would sound pretty probative to me.


*