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Posted: 12/3/2005 7:31:15 AM EDT
Physics of the Ballistic Pressure Wave

One might wonder why a given 135 grain .40 caliber JHP bullet at 1350 FPS creates a larger ballistic pressure wave many other JHP bullets in the .40 S&W cartridge.

The origin of the pressure wave is Newton’s third law. The bullet slows down in tissue due the force the tissue applies to the bullet. By Newton’s third law, the bullet exerts an equal and opposite force on the tissue. When a force is applied to a fluid or a visco-elastic material such as tissue or ballistic gelatin, a pressure wave radiates outward in all directions from the location where the force is applied.

The instantaneous magnitude of the force, F, between the bullet and the tissue is given by

F = dE/dx,

Where E = ½ m V*V is the instantaneous kinetic energy of the bullet, and x is the penetration distance. dE/dx is the first derivative of the energy with respect to the penetration depth. In other words, it is the instantaneous rate of kinetic energy loss per inch of penetration depth. Losing 100 ft-lbs of kinetic energy in 0.02 feet of penetration would create a force of 5,000 lbs because 100 ft-lbs/0.02 ft = 5,000 lbs.

It is important to note that this force (equal to the rate of energy loss) changes continuously and depends on both the loss of velocity and the loss of mass (unless the mass is constant). By the chain rule of calculus,

F = dE/dx = ½ V*V dm/dx + m V dV/dx,

Where dm/dx and dV/dx are the instantaneous rate of mass and velocity loss with respect to penetration depth.

Applying this formula directly requires detailed knowledge of the instantaneous mass and velocity changes of a bullet at every point along the wound channel. The instantaneous force can be accurately determined by shooting the same bullet through varying thicknesses of ballistic gelatin. In other words, one might shoot through a 0.05 ft thick block of gelatin to determine the loss of energy in the first 0.05 ft of penetration. Then one might shoot through a 0.1 ft thick block of gelatin to determine the loss of energy in a 0.1 ft thick block of gelatin. Then one might shoot through a 0.15 ft thick block of gelatin to determine the loss of energy in a 0.15 ft thick block of gelatin. Repeating this process in small increments, and applying standard techniques for estimating derivatives from measured values at closely spaced points would yield an accurate measurement of the instantaneous force at every penetration depth.

There are some simple and reasonable estimates that can be made more easily.

In cases where the mass is constant, the average force Fave between the tissue and bullet is simply the initial kinetic energy E divided by the penetration depth d.

Fave = E/d.

However, in cases where the bullet loses mass along the wound channel, the average force is increased by between 1 and 2 times the fraction of mass lost. If the bullet loses 20% of its mass distributed evenly along the wound channel, it creates an average force

Fave = 1.2 E/d.

Many bullets which lose mass, lose more mass early in the wound channel rather than late. This can enhance the average force even more. If the average depth of lost mass is one third of the penetration depth (d/3), the enhancement of the average force is twice the lost mass fraction. In other words, a bullet which loses 20% of its mass at an average depth of one third the penetration depth will create an average force

Fave = 1.4 E/d.

The peak of any variable force is larger than the average value. The peak to average ratio usually occurs during or right after expansion, and most bullets have peak to average force ratios between 3 and 8. Bullets which do not expand, penetrate deeply, and lose energy gradually have a peak to average ratio close to 3. Bullets which expand rapidly, lose a lot of energy early, erode down to a smaller diameter and then penetrate deeply have a peak to average ratio close to 8. Nosler Partitions with their soft lead front section which expands rapidly and erodes away quickly leaving the base containing roughly 60% of the original mass at little more than the unexpanded diameter is an example of large peak to average force ratio. Most JHP handgun bullets have a peak to average ratio close to 5, so this can provide a reasonably accurate estimate of the peak force in many cases.

If we go with the more conservative estimate that the average distance of penetration for lost mass is the middle of the total penetration (d/2) and we call the faction of lost mass f, then we estimate the peak pressure as

Fpeak = (1 + f) 5 E/d,

This allows us to see quite simply why the 135 grain bullet has a larger peak force than other .40 caliber S&W loads. The table below shows values of mass, energy, penetration, fraction of lost mass, and the peak force estimate for several .40 S&W loads

Load m (gr) V (FPS) d (in) E (ft-lbs) f F (lbs)
DT135JHP(N) 135 1350 11.9 547 0.36 3752
Rem165GS 165 1150 12 485 0 2427
Fed155HS 155 1140 13.3 448 0 2021
Fed180HS 180 950 15 361 0 1445

This force acts as a point of origin for the pressure wave which radiates outward in all directions. The pressure falls off with distance because the area it covers increases. However, we can compare the peak pressure generated by different loads if we standardize the point of interest to be the surface of a sphere with diameter of 1” centered at the point of origin of the force. This gives peak pressure wave levels of the different loads:

Load P(1") PSI
DT135JHP(N) 1195
Rem165GS 773
Fed155HS 643
Fed180HS 460

In summary, the .40 S&W Double Tap loading of the Nosler 135 grain JHP has a larger pressure wave than many other JHP bullets in that cartridge for three reasons:

1. It has greater kinetic energy.
2. It penetrates less.
3. It fragments and loses more of its mass.

One can apply this identical analysis to other JHP loads in this and other cartridges. Doing so reveals that there are a few other JHP loads which generate comparable peak pressure levels. Among them are the 125 grain Federal and Remington JHP loads in .357 Magnum that are known for their ability to incapacitate quickly.

Michael Courtney
Link Posted: 12/3/2005 12:52:00 PM EDT
Will there be a test?
Link Posted: 12/3/2005 7:06:42 PM EDT
Is the pressure wave a sonic wave or a fluid wave?
Link Posted: 12/4/2005 6:31:31 AM EDT
Dude, put down your calculus book and have a smoke.

Link Posted: 12/4/2005 12:03:27 PM EDT

Originally Posted By PAEBR332:
Is the pressure wave a sonic wave or a fluid wave?



The pressure wave has both sonic and fluid components. There is a stress component also. In other words, the pressure wave is the force per unit area that would be measured by a high-speed pressure sensor.

Michael Courtney
Link Posted: 12/7/2005 10:47:02 PM EDT
[Last Edit: 12/7/2005 10:56:16 PM EDT by chewbacca]
What is the penetration in inches of the 135 gr in ballistic gel?

Also, what physical effect does the pressure wave have on tissue? Fackler demonstrated that the transfer of KE doesn't mean much because tissue is so elastic, it merely stretches then returns more or less to its original shape, thereby not increasing the permanent wound channel and thus not increasing the lethality of the projectile.
Link Posted: 12/8/2005 2:34:08 AM EDT

Originally Posted By chewbacca:
What is the penetration in inches of the 135 gr in ballistic gel?



10-12"



Originally Posted By chewbacca:
Also, what physical effect does the pressure wave have on tissue?



Physical effects range from pulverization to hemorrhaging.


Originally Posted By chewbacca:
Fackler demonstrated that the transfer of KE doesn't mean much because tissue is so elastic, it merely stretches then returns more or less to its original shape, thereby not increasing the permanent wound channel and thus not increasing the lethality of the projectile.



We're interested in rapid incapacitation, not eventual lethality. Also, unlike Fackler, we're not committed to the unproven presupposition that rapid incapacitation can only occur via wounding that is easily detected by a trauma surgeon or medical examiner long after the gun fight is over. We are keeping our minds open to the possibility that there could be rapid incapacitation mechanisms that don't leave a lot of tissue damage.

Finally, it sould also be noted that Fackler's demonstration that "[tissue] merely stretches then returns more or less to its original shape" was limited to hangun bullets with smaller pressure waves than those we are looking at. I haven't seen any published work where Fackler of any other researcher systematically shows that handgun loads with comparable pressure waves do not cause an increase in the permanent wound channel. It seems unfounded to extrapolate results from handgun loads with significantly smaller pressure waves.

Michael Courtney
Link Posted: 12/8/2005 10:28:30 AM EDT
[Last Edit: 12/8/2005 10:28:56 AM EDT by chewbacca]
I have seen Fackler's pics (not drawings) of tissue after it has been hit by a 5.45X39, and there was only a small amount of damage resulting from the temporary cavity (transfer of KE). I am very interested in your work, for terminal ballistics has always been a hobby, but how are/can you measure these " pressure effects" if you do not know what they are and they cannot be detected via autopsy?
Link Posted: 12/8/2005 6:00:47 PM EDT
tag
Link Posted: 12/8/2005 6:01:57 PM EDT
[Last Edit: 12/8/2005 6:03:50 PM EDT by Lumpy196]
Link Posted: 12/8/2005 6:27:08 PM EDT

Originally Posted By Lumpy196:



He's using math. I don't believe in math. Instead of making me agree with him, because I can't disprove his equations, he has me saying "Show me the Gel!"
Link Posted: 12/9/2005 5:51:57 AM EDT

Originally Posted By chewbacca:
I have seen Fackler's pics (not drawings) of tissue after it has been hit by a 5.45X39, and there was only a small amount of damage resulting from the temporary cavity (transfer of KE). I am very interested in your work, for terminal ballistics has always been a hobby, but how are/can you measure these " pressure effects" if you do not know what they are and they cannot be detected via autopsy?



The effect of the pressure wave is to cause more rapid incapacitation. This can be measured in live animal experiments by applying the pressure wave to a test subject and measuring how rapidly incapacitation occurs. We've observed these effects directly in experiments that are in preparation for publication.

One can also show that the average incapacitation times from the Strasbourg Goat Tests are well correlated with the peak pressure wave magnitude. Our own experiments demonstrate both the validity of the Strasbourg Tests as well as the accuracy of the average incapacitation times reported.

Finally, one can also show that the Marshall and Sanow data demonstrates a good correlation between pressure wave magnitude and relative load effectiveness.

Our pressure wave models make specific quantitative predictions on how pressure wave effects decrease incapacitation time in humans hit near the center of the chest. The recent increase in surveillance systems means that more and more shooting events are being recorded on audio and video. Consequently, within a few years forensic analysis will be able to accurately reconstruct the detailed time line of gunfights sufficiently for testing the pressure wave model and its predictions for rapid incapacitation in humans.

Michael Courtney

Link Posted: 12/13/2005 11:36:50 AM EDT

The effect of the pressure wave is to cause more rapid incapacitation. This can be measured in live animal experiments by applying the pressure wave to a test subject and measuring how rapidly incapacitation occurs. We've observed these effects directly in experiments that are in preparation for publication.


When you get your findings published please post a link or way to find them. I'd be interested in what you come up with. Thanks.
Link Posted: 12/16/2005 6:18:56 PM EDT

Originally Posted By Michael_Courtney:

Originally Posted By chewbacca:
I have seen Fackler's pics (not drawings) of tissue after it has been hit by a 5.45X39, and there was only a small amount of damage resulting from the temporary cavity (transfer of KE). I am very interested in your work, for terminal ballistics has always been a hobby, but how are/can you measure these " pressure effects" if you do not know what they are and they cannot be detected via autopsy?



The effect of the pressure wave is to cause more rapid incapacitation. This can be measured in live animal experiments by applying the pressure wave to a test subject and measuring how rapidly incapacitation occurs. We've observed these effects directly in experiments that are in preparation for publication.

One can also show that the average incapacitation times from the Strasbourg Goat Tests are well correlated with the peak pressure wave magnitude. Our own experiments demonstrate both the validity of the Strasbourg Tests as well as the accuracy of the average incapacitation times reported.

Finally, one can also show that the Marshall and Sanow data demonstrates a good correlation between pressure wave magnitude and relative load effectiveness.

Our pressure wave models make specific quantitative predictions on how pressure wave effects decrease incapacitation time in humans hit near the center of the chest. The recent increase in surveillance systems means that more and more shooting events are being recorded on audio and video. Consequently, within a few years forensic analysis will be able to accurately reconstruct the detailed time line of gunfights sufficiently for testing the pressure wave model and its predictions for rapid incapacitation in humans.

Michael Courtney




Who do you mean when you say 'we'? And what Marshall and Sanow 'data' are you talking about? The data that they won't share with anyone? What ammo company do you work for, and what product are you trying to sell?
Link Posted: 12/19/2005 4:44:08 AM EDT

Originally Posted By Sparky315:
Who do you mean when you say 'we'?



We are the Ballistic Testing Group, a group of scientists working on a number of projects in internal, external, terminal, and forensic ballistics.


Originally Posted By Sparky315:
And what Marshall and Sanow 'data' are you talking about?



The data they have published in three stopping power books. Anyone can access these books and verify our findings once our models are published.



What ammo company do you work for,



We are not supported in any way by any ammo company.



and what product are you trying to sell?



Good, sound science is our only product. We conduct research and we publish our findings.

We have no financial interest in any gun industry company. One of our scientists owned stock in a gun company early in the project, but a requirement for participation was that every scientist on our team sell any and all holdings in gun industry companies prior to initial publication of our findings, and this has been done.

Michael Courtney
Link Posted: 12/19/2005 4:57:47 AM EDT
.
Link Posted: 12/19/2005 5:25:28 AM EDT
[Last Edit: 12/19/2005 5:26:17 AM EDT by PAEBR332]

Originally Posted By Michael_Courtney:
<snip>

Originally Posted By Sparky315:
And what Marshall and Sanow 'data' are you talking about?



The data they have published in three stopping power books. Anyone can access these books and verify our findings once our models are published.

<snip>.

Michael Courtney



You have posted information about a LINEAR regression model for pressure wave magnitude and incapacitation time your team has developed. The M&S data is binomial in nature (Stop or fail to stop). In order to compare the continuously variable pressure wave magnitude input factor to the binomial output factor of the M&S study, you should perform a binary logisitic regression study. If you have done such a study, please post your results, particularly the P-value and and the Odds Ratio for the test. Alternatively, you could perform a discriminant analysis and post those results.

If this study has not been done, please explain what statistical test your team did, at what significance level, and the resultant P-value, to show a significant correlation between pressure wave magnitude and OSS percentage.
Link Posted: 12/20/2005 1:33:06 PM EDT

Originally Posted By PAEBR332:
You have posted information about a LINEAR regression model for pressure wave magnitude and incapacitation time your team has developed.



As usual, you are misrepresenting what we have done. Our regression model is non-linear.


Originally Posted By PAEBR332:
The M&S data is binomial in nature (Stop or fail to stop). In order to compare the continuously variable pressure wave magnitude input factor to the binomial output factor of the M&S study, you should perform a binary logisitic regression study. If you have done such a study, please post your results, particularly the P-value and and the Odds Ratio for the test. Alternatively, you could perform a discriminant analysis and post those results.



I have published numerous articles in the peer reviewed journals where a discrete variable is modeled with a continuous function, including discrete variables that result from binomial events.

There are many measures of goodness of fit for comparing continuous models with probabilities determined from binomial observations. We have studied a number of them in this case.

However, publishing every possible measure of goodness of fit can be distracting in an article of more general interest. Our intent is to publish a few standard indicators of goodness of fit, and provide sufficient information for interested third parties to compute whatever other measures they desire. Regardless of what measures of goodness of fit one publishes there is almost always someone who wants to see a different one.

It is generally considered sufficient to include a couple of standard measures, along with sufficient information for the interested reader to compute others if he desires. Most readers can make the most sense from correlation coefficients and from the standard error, which gives a quantitative sense of the model's predictive accuracy.

Michael Courtney
Link Posted: 12/20/2005 5:02:51 PM EDT

Originally Posted By Michael_Courtney:

Originally Posted By PAEBR332:
You have posted information about a LINEAR regression model for pressure wave magnitude and incapacitation time your team has developed.



As usual, you are misrepresenting what we have done. Our regression model is non-linear. Funny, in your earliest post heere on ARFCOM, you stated that the realtionship is linear. You even talked about the Pearson R Correlation Coefficient, which is a measure of LINEAR correlation. Try keeping your story straight. Or better yet, get it PUBLISHED so people can read the details, instead of select snippets you choose to post.


Originally Posted By PAEBR332:
The M&S data is binomial in nature (Stop or fail to stop). In order to compare the continuously variable pressure wave magnitude input factor to the binomial output factor of the M&S study, you should perform a binary logisitic regression study. If you have done such a study, please post your results, particularly the P-value and and the Odds Ratio for the test. Alternatively, you could perform a discriminant analysis and post those results.



I have published numerous articles in the peer reviewed journals where a discrete variable is modeled with a continuous function, including discrete variables that result from binomial events.

There are many measures of goodness of fit for comparing continuous models with probabilities determined from binomial observations. We have studied a number of them in this case.

However, publishing every possible measure of goodness of fit can be distracting in an article of more general interest. Our intent is to publish a few standard indicators of goodness of fit, and provide sufficient information for interested third parties to compute whatever other measures they desire. Regardless of what measures of goodness of fit one publishes there is almost always someone who wants to see a different one.

It is generally considered sufficient to include a couple of standard measures, along with sufficient information for the interested reader to compute others if he desires. Most readers can make the most sense from correlation coefficients and from the standard error, which gives a quantitative sense of the model's predictive accuracy.

Michael Courtney



Until you PUBLISH the information in sufficient detail, all we have is your unsubstantiated claim as to goodness of fit, etc. You have been unwilling to release any details, claiming it is detrimental to your funding, etc. Either stop posting "We found something earth-shaking, but cannot give you any details, just trust me," or GET IT INTO PRINT. You have been posting about this study on various internet forums now for well over a year. Time to get it into print.

It is particularly troubling that you claim your study will fundamentally alter the way people protect themselves with handgun rounds (a true life-and-death issue for many), but are unwilling to put the information out in enough detail for people to make an informed decision on whether or not your claims have validity. Instead, you post on various internet forums, claim to be the only expert in the field, and charge all who oppose you with being uniformed (of your still secret findings).
Link Posted: 12/21/2005 4:42:33 AM EDT

Originally Posted By PAEBR332:
Funny, in your earliest post heere on ARFCOM, you stated that the realtionship is linear. You even talked about the Pearson R Correlation Coefficient, which is a measure of LINEAR correlation. Try keeping your story straight. Or better yet, get it PUBLISHED so people can read the details, instead of select snippets you choose to post.



I never stated that the relationship is linear. You are welcome to re-post the material where you claim I said the relationship is linear. I also never talked about a "Pearson R Correlation Coefficient." I simply mentioned "Correlation Coefficient." A "Correlation Coefficient" can be determined from non-linear models.


Originally Posted By PAEBR332:
It is particularly troubling that you claim your study will fundamentally alter the way people protect themselves with handgun rounds (a true life-and-death issue for many),



Please provide a reference to where I have made this claim. The fact is that I have not made this claim. Your misrepresentation continues.


Originally Posted By PAEBR332:
but are unwilling to put the information out in enough detail for people to make an informed decision on whether or not your claims have validity.



I am not unwilling. I have stated repeatedly that our work is in preparation for publication. Most scientists understand that the publication process takes some time, and that there is a difference between preparing work for publication and being "unwilling to put the information out."


Originally Posted By PAEBR332:
Instead, you post on various internet forums,



There's a difference between "instead" (of publishing) and "until" (the details are published). The information is also being shared privately with other scientists and researchers.


Originally Posted By PAEBR332:
claim to be the only expert in the field,



Please provide a reference for this claim. You can't because your claim is false. I've acknowledged important contributions of Fackler (penetration in gel matches tissue), MacPherson (_Bullet Penetration_), Marshall, Sanow, Roberts, and the authors of the Strasbourg Goat Tests. I would consider all these folks experts in the field, along with Roberts and others.

I do make an important distinction between accepting viewpoints based on "expert opinion" and in accepting findings based on repeatable experiments. Most good scientists show a strong preference for repeatable experiment over expert opinion.


Originally Posted By PAEBR332:
and charge all who oppose you with being uniformed



Please provide a reference for this claim. You can't because your claim is false.

Michael Courtney
Link Posted: 12/21/2005 6:43:39 AM EDT
Once again, you protest too much. Because you refuse to divulge simple information, like what SPECIFiC statistical test was run, at what significance level, and what the resultant p-vlaue was, I have been having to make ASSUMPTIONS about the exact test being done. Instead of making us play 20 questions, you could simply state something like: "Our team developed a quadratic regression model that shows... The test is significant and the 5% level." Instead, you use overly generic terms like regression model (what kind? Linear? Quadratic? Cubic? Non-parametric?) and level of uncertainty (defined how? Is it standard deviation? Range? What?). And how about answering the question I have asked multiple times: What kind of sample sizes were used in your deer study? Just give us a range. Less than 5 for each tested round? 5 to 10? 11 to 20? More than 20?

As for my statment about your claim of sole expertise, I stick by it. I am referring specifically to the effects of the pressure wave. You continue to make claims that the pressure wave is a VERY important incapacitation mechanism, but without anything other than your posts on the internet to back it up. This is nothing more than an appeal to authority (your own), for one without any as yet proven claim to authority on the topic. You have glibly dismissed Fackler, MacPherson, and any others who claim that the pressure wave has been found to be an unimportant wounding mechanism. The older study by Harvey et al on the effects of the pressure wave seems to directly contradict your study, but I am sure you will address that issue once you publish.
Link Posted: 12/22/2005 5:56:14 AM EDT
[Last Edit: 12/22/2005 6:02:33 AM EDT by Michael_Courtney]

Originally Posted By PAEBR332:
As for my statment about your claim of sole expertise, I stick by it. I am referring specifically to the effects of the pressure wave. You continue to make claims that the pressure wave is a VERY important incapacitation mechanism, but without anything other than your posts on the internet to back it up.

This is nothing more than an appeal to authority (your own)



Not at all. My findings are in substantial agreement with those of the Strasbourg Goat Tests, which I have mentioned repeatedly.


Originally Posted By PAEBR332:
You have glibly dismissed Fackler, MacPherson, and any others who claim that the pressure wave has been found to be an unimportant wounding mechanism.



Questioning expert opinions that are made without reference to experimental data is not a "glib dismissal."

Questioning expert opinions that are made without reference to experimental data is a key part of the scientific method.

Also, I have pointed out that Fackler and MacPherson rely too heavily on their unproven presupposition that easily detectable wounding is necessary for an effect to contribute to incapacitation.

I have also pointed out that the assertions that Facker and MacPherson make regarding lithotriptor pressure waves not causing wounding have been experimentally shown to be false.

Thus my questioning of the Fackler and MacPherson assertion that the pressure wave does not contribute to incapacitation via handgun bullets is not "glib dismissal", but rather it has sound scientific reasoning behind it.


Originally Posted By PAEBR332:
You continue to make claims that the pressure wave is a VERY important incapacitation mechanism, but without anything other than your posts on the internet to back it up.



First of all, let me say that we have not claimed that the pressure wave is a "VERY important incapacitation mechanism" but only that it can make significant and measurable contributions to incapacitation. In other words, incapacitation is better explained by considering both pressure wave and crush cavity than by considering crush cavity alone.

Our work is in preparation for publication. We have circulated our first draft among scientists, engineers, medical professionals, and mathematicians.

Other than my discussion of our own work, I have referred to the Strasbourg Goat Tests which are in substantial agreement with our work regarding the pressure wave effects. So you are misrepresenting the situation to assert that my case is "without anything other than your posts on the internet to back it up." In answering the Fackler/MacPherson claim that the pressure wave of the lithotriptor does not cause any wounding, I have also referred to published experiments showing that the lithotriptor can, in fact, cause wounding.


Originally Posted By PAEBR332:
The older study by Harvey et al on the effects of the pressure wave seems to directly contradict your study, but I am sure you will address that issue once you publish.



If you would like me to specifically address a previous work, you should give a complete reference.

There are numerous papers in the literature which claim to disprove pressure wave incapacitation effects. These papers usually contain one or more of the following flaws:

1. Considering velocity ranges rather than pressure wave magnitude ranges. There is no velocity threshold where the pressure wave effects begin to turn on. There is a pressure wave magnitude threshold.

2. Considering observable wounding rather than a measure of incapacitation. It is important to consider the possibility of a incapacitation mechanisms that might not produce wounding that is easily detectable to a trauma surgeon or medical examiner. Consequently, to disprove the pressure wave hypothesis, one would have to observe and measure incapacitation directly rather than simply observing wounding after the fact. To my knowledge, there is no published data that fails to show a pressure wave contribution to incapacitation over the full range of peak pressure magnitudes produced by handgun loads. Please enlighten me if you know of something I don't.

3. Showing that the pressure wave does not make a noticable contribution to incapcitation in a pressure wave regime considerably smaller than some available handgun loads. To compare different handgun loads, we consider the peak pressure on the edge of a 1" diameter circle centered on the axis of the wound channel. Handgun loads which produce 500 PSI at this point have pressure wave incapacitation effects that are difficult to discern (require a very large number of data points). Handgun loads which produce over 1000 PSI at this point and penetrate at least 10" have pressure wave contributions that are relatively easy to discern (don't require as many data points.)

4. Confusing the concepts of unproven with disproven. The fact that previous studies make a weak case for the pressure wave mechanism, means that the effect has not yet been proven in the published literature. This does not mean it has been disproven.

5. Considering kinetic energy ranges rather than pressure wave ranges. In other words, it is not sufficient to show the absence of a pressure wave contribution to incapacitation with loads that produce 500 ft-lbs of kinetic energy, one needs to show the absence of a pressure wave contribution to incapacitation with loads that produce 1000 PSI on the edge of a 1" diameter circle centered at the wound channel.

6. Considering only the "sonic pressure wave" rather than the complete pressure wave (defined as the force per unit area that would be measured by a high-speed pressure transducer).

If the "Harvey, et al." paper to which you refer is more significant than a rehash of these common flaws, I will gladly consider it carefully and provide some comments here when I have an opportunity.

Michael Courtney
Link Posted: 12/22/2005 6:21:58 AM EDT
Strasbourg? OMG.

I know you know the Harvey article. You had an argument with Shawn Dodson last year over on GlockTalk about that study.

And for about the tenth time, you avoid answering my question about sample sizes. Why?

Oh, BTW, was each deer shot, and the distance measured in the presence of more than one member of the team? Again, a very simple question. You already admitted that the shooter knew which round was being used for each shot and measurement, a violation of good blinding protocols. That's right, your study does not need to be blinded because it is totally immune to unintentional (or intentional) bias in data collection.

As for misrepresenting you, sorry if you feel that way. In the first thread on ARFCOM in which you mentioned your study, your were VERY dismissive of Fackler, [et.al.. You made claims that the pressure wave and TSC were very important to incapacitation, and that those who dismiss it are ill-informed (of your yet-to-be-published study). This thread is currently not available online due to a server problem that Goatboy is trying to fix. Once it is back up, I can quote your statements if you like. Touchy aren't you?
Link Posted: 12/22/2005 7:57:05 AM EDT
[Last Edit: 12/22/2005 8:34:53 AM EDT by Michael_Courtney]

Originally Posted By PAEBR332:
I know you know the Harvey article. You had an argument with Shawn Dodson last year over on GlockTalk about that study.



I am not saying that I am unaware of a particular article, just trying to nail down which article to which you are referring. When asking someone to comment on an article, it is customary to give a complete reference (authors, journal, date or volume, title), not just one author and the general subject area.

I have discussed things with Dodson on the GlockTalk forum. Here is his reference to Harvey, et al from the Glocktalk thread:


Shawn Dodson
http://www.glocktalk.com/showthread.php?s=&postid=3448687#post3448687

The sonic pressure wave (sound wave in soft tissues = 4X the speed of sound in air) is ruled out by: 1) Harvey, et al: "Secondary Damage in Wounding Due to Pressure Changes Accompanying the Passage of High Velocity Missiles," Surgery 1946; 21: 218-239, and 2) the lithotriptor.



Now that I am aware of the specific paper you are referring to, it is possible to point out that this specific paper fails to disprove the pressure wave hypothesis because it contains all six of the flaws I mentioned earlier:

1. Considering velocity ranges rather than pressure wave magnitude ranges. There is no velocity threshold where the pressure wave effects begin to turn on. There is a pressure wave magnitude threshold.

2. Considering observable wounding rather than a measure of incapacitation. It is important to consider the possibility of a incapacitation mechanisms that might not produce wounding that is easily detectable to a trauma surgeon or medical examiner. Consequently, to disprove the pressure wave hypothesis, one would have to observe and measure incapacitation directly rather than simply observing wounding after the fact. To my knowledge, there is no published data that fails to show a pressure wave contribution to incapacitation over the full range of peak pressure magnitudes produced by handgun loads. Please enlighten me if you know of something I don't.

3. Showing that the pressure wave does not make a noticable contribution to incapcitation in a pressure wave regime considerably smaller than some available handgun loads. To compare different handgun loads, we consider the peak pressure on the edge of a 1" diameter circle centered on the axis of the wound channel. Handgun loads which produce 500 PSI at this point have pressure wave incapacitation effects that are difficult to discern (require a very large number of data points). Handgun loads which produce over 1000 PSI at this point and penetrate at least 10" have pressure wave contributions that are relatively easy to discern (don't require as many data points.)

4. Confusing the concepts of unproven with disproven. The fact that previous studies make a weak case for the pressure wave mechanism, means that the effect has not yet been proven in the published literature. This does not mean it has been disproven.

5. Considering kinetic energy ranges rather than pressure wave ranges. In other words, it is not sufficient to show the absence of a pressure wave contribution to incapacitation with loads that produce 500 ft-lbs of kinetic energy, one needs to show the absence of a pressure wave contribution to incapacitation with loads that produce 1000 PSI on the edge of a 1" diameter circle centered at the wound channel.

6. Considering only the "sonic pressure wave" rather than the complete pressure wave (defined as the force per unit area that would be measured by a high-speed pressure transducer).



Originally Posted By PAEBR332:
And for about the tenth time, you avoid answering my question about sample sizes. Why?



And how many times till you continue to ignore my reference to an non-disclosure agrement that prevents release of certain details prior to publication?

I have told you why, and you continue to pretend I have not. Why do you pretend I have not already answered this question?

Why don't you contact an company that does live animal testing on cosmetics, refuse to identify yourself, and then demand information on their sample sizes? Would you be correct in concluding that their results are invalid because they won't divulge sample size information to an anonymous person? Maybe you're just an animal-rights activist trying to figure out if their operation is large enough to warrant an attack. It makes some sense not to release sample sizes prior to publication.

In addition, I have given an estimate of our uncertainty of average incapacitation distance using standard methods. From this information, it would not be too difficult for a trained statistician to estimate sample sizes.

Of course, someone who only claims to be a statistician but has problems distinguishing the difference between unproven and disproven might have some trouble.

Someone who claims to be a statistician, but cannot see that modeling a probability with a linear, quadratic, or cubic equation cannot provide the proper limiting behavior might have some difficulty.


Originally Posted By PAEBR332:
Again, a very simple question. You already admitted that the shooter knew which round was being used for each shot and measurement, a violation of good blinding protocols.



One only needs a blinding protocol for observations which have some subjective component. Measurement of where the bullet hits is completely objective, so that any shot-placement bias could be detected. The location of each bullet placement was carefully measured and recorded, so that the possibility of bias can be objectively excluded.

At least two scientists were present for each test subject kill, carcass recovery, distance measurement, and necropsy.

My comments on Fackler and earlier researchers have been measured and largely in the same tone as in my last post. I question the validity of conclusions they have reached without the benefit of repeatable experiments, and I point out the assertions they have made which were later proven incorrect in the peer-reviewed literature.

My comments on the importance of the TSC and the pressure wave have likewise been measured to the degree that I have always acknowedged that the permanent crush cavity plays an important role in incapacitation. A goal of our study is to understand the relative contributions of different mechanisms, and we believe that there are cases where the pressure wave plays a more significant role in rapid incapacitation than the permanent crush cavity.

However, the relative importance of the different mechanisms depends heavily on the particular load being discusses. The pressure wave mechanism is relatively unimportant for .380 ACP loadings of FMJ bullets, and I have pointed this out explicitly in earlier discussions. The pressure wave is more important in for the 135 grain Nosler JHP in .40 S&W.

I have certainly never said that the pressure wave is "VERY important" for any and all handgun loads. The point is that is can have a significant contribution for SOME handgun loads.

Michael Courtney
Link Posted: 12/22/2005 10:30:46 AM EDT
[Last Edit: 12/22/2005 10:55:49 AM EDT by PAEBR332]
If you are under a non-dislcosure agreement, then stop blabbing on the internet. Since you cannot reveal critical data about your study, your claims can neither be confirmed nor refuted. They are simply claims on the internet.

Dr. Fackler, Dr. Roberts, Gene Wolberg, Shawn Dodson, Duncan MacPherson: All have published extensively on wound ballistics. You have as yet published NOTHING in the field. Perhaps it would be a better tactic to get your study published PRIOR to telling everyone via the internet that all of these people are wrong in important ways. You have made ammunition recommendation on this website that are in direct conflict with the recommedations of the above. You have recommended ammunition that fails to meet FBI and IWBA specifications on penetration, but that produces a large pressure wave.
Link Posted: 12/22/2005 12:59:44 PM EDT

Originally Posted By PAEBR332:
If you are under a non-dislcosure agreement, then stop blabbing on the internet. Since you cannot reveal critical data about your study, your claims can neither be confirmed nor refuted. They are simply claims on the internet.



It is customary in every field of science to discuss findings in informal settings as part of the process of preparing works for publication.

You've got a chicken and egg problem if you insist that work be published before discussing it in informal settings.

We were careful before entering into a non-disclosure agreement to frame that agreement in such a way that many of the important aspects could be discussed in a public manner once certain stages of the research were completed but prior to publication. Other details must wait for publication, and there are some details (that are not necessary to weigh the scientific validity of the work) may never be released. This is the case in many areas of science covered by non-disclosure agreements.

There are many researchers and interested parties who appreciate whatever access can be gained to scientific results prior to publication. As a result of the informal discussions, we have been able to make suggestions to the experimental designs so that independent research results can be more easily compared with ours. We have also received valuable input and suggestions to future experimental designs, as well as quite a bit that is relevant to the manner in which we communicate our findings.

The claims we have made can be confirmed or refuted by attempts to repeat our work. We have already released sufficient information on our experimental procedure to do this.



Originally Posted By PAEBR332:
Dr. Fackler, Dr. Roberts, Gene Wolberg, Shawn Dodson, Duncan MacPherson: All have published extensively on wound ballistics.

You have as yet published NOTHING in the field. Perhaps it would be a better tactic to get your study published PRIOR to telling everyone via the internet that all of these people are wrong in important ways.



None of these researchers is wrong in any matter where they can directly reference repeatable experiments in direct support of their assertions.


Originally Posted By PAEBR332:
You have made ammunition recommendation on this website that are in direct conflict with the recommedations of the above. You have recommended ammunition that fails to meet FBI and IWBA specifications on penetration, but that produces a large pressure wave.



The FBI specification is for law enforcement use. I have tried to be clear in my recommendations that most law enforcement uses and applications and risk assessments that require 12" of penetration are not met by the recommendations I have made regarding the use of expanding JHP bullets in .380 ACP, and of the Triton Quik-Shok in .357 Sig.

Recommending any bullet begins with an assessment of the application and risk assessments. Most law enforcement uses require 12" of penetration. I have never suggested otherwise.

Whether or not a particular CHL-holder has an application that requires this level of penetration is up to the application and risk assessment of that particular CHL holder. I recommend closer to 10" of penetration for applications and risk assessments where frontal shots are more likely than shots from the side, or in crowded situations where there is significant risk of injury to innocent bystanders if a bullet exits the target.

The recommendation of loads that penetrate 10" for some CHL risk assessments may indeed contradict some experts in the field. However, these experts made their recommendations under the mistaken presupposition that the pressure wave does not provide a contribution to rapid incapacitation. We have substantial evidence that it does.

Some might prefer to stick with the opinion of the established experts. That's fine. Some folks prefer to at least be given information relevant to considering other viewpoints.

Michael Courtney
Link Posted: 12/23/2005 8:11:39 AM EDT
Can you cite a source that holds the 12" minimum is a LEO only standard?

Dr. Courtney, I am tired of this. Until you get your study PUBLISHED, it is pointless. From the information you have divulged, you and your team appear to have ignored NUMEROUS confounding factors. We shall see what happens once it's published.

Link Posted: 12/23/2005 2:22:02 PM EDT
Given the confounding factors, one might wonder why bother to study handgun bullet effectiveness. There certainly are more important aspects of surviving lethal force encounters:
· Avoidance (You win every gun fight you avoid, the best you can do is survive the gun fights for which you are present.)
· Training (Learning to avoid getting shot is very important, as is learning to put your bullets where they need to go.)
· Bringing a gun (Don’t get caught in a lethal force encounter without one.)

There are so many complicating factors to bullet effectiveness that one might consider only preparing for the most important aspects. But take a minute and put yourself in the shoes of the person selecting the ammo for a large law enforcement agency that will probably have hundreds of lethal force encounters each year for the foreseeable future.

After you do the best job you can on the training side of the equation, you need to decide what ammo your law enforcement agents are going to carry in their guns. Regardless of how good the shot placement is that results from your training program and officer diligence, your choice of ammo will probably make a difference in at least some fraction of those lethal force encounters, because it will play a role in determining how long some of the bad guys will remain capable of shooting back at the good guys.

If your agency is involved in 1000 gun fights during the length of service of a particular choice of ammo, and the choice of ammo you selected has a bearing on the outcome only 2% of the time, then the choice you made in ammo selection will affect 20 gunfights. That is sufficient motivation for us to do a good job developing scientific methods for understanding and testing ammo effectiveness.

Also consider the possibility of a day when terrorists in the form of active shooters and bombers are a regular occurrence on our native soil. Since Columbine, the common law enforcement strategy has evolved from calling the SWAT team to having the first responding officers form a contact team of three to four officers and attempt to quickly incapacitate the active shooters. In many cases, these officers will be armed with handguns. Improving the effectiveness of handgun ammunition to rapidly incapacitate a terrorist or active shooter will pay dividends in shortening the time active shooters have to harm our citizens and responding officers.

Some folks shy away from attempts to quantify bullet performance because complicating factors and varying individual reactions necessitate a probabilistic approach. Some go so far as to suggest that quantification of bullet performance is scientifically intractable because of the large variations in the target reaction to being shot. However, science makes substantial progress in many areas that have a wide variety of individual response to the stimulus being studied.

For example, different individuals each have different genetic predispositions to cancer. Environmental factors further complicate the issue. There is a wide range of variation. This does not mean that a scientific study cannot determine the probability curve for contracting cancer after smoking Brand X for a certain number of years.

Suppose a scientific study compares the probabilities for contracting cancer after smoking Brand X for a certain number of years and smoking Brand Y for a certain number of years. In spite of complicating factors from the genetic and environmental variations in the specific cases, such a study can be done, and would constitute a valid scientific basis for concluding that Brand X creates a higher or lower cancer risk than Brand Y.

This same kind of study can conclude that exposure to sunlight increases cancer risk over time, or that certain foods can reduce the risk of certain cancers. In each case, there are broad variations in genetic and environmental factors, but sufficient numbers of data points can effectively average over these factors and understand how the variable of interest affects the outcome.

This kind of research does not claim that the outcome can be predicted for a specific individual, but only that the percentage of outcomes can be predicted for a large number of individual events. The fact that the outcome cannot be predicted for a specific individual does not mean that one cannot increase his odds of living to a ripe old age by certain choices such as quitting smoking or wearing sunscreen.

Likewise, one can increase ones chances of surviving a gunfight with a better ammo choice.

Probability theory correctly predicts that almost anyone who spends enough time and money gambling as a customer in a casino will come out on the losing end, and that the owners of the casino will come out on the winning end. The outcome of any specific bet is not predictable, but the eventual outcome of a large number of bets is predictable, and one of the authors (MC) often tells his college level statistics students that the lottery is a tax on people who are poor at math.

Confounding factors exist in many areas of research, but a combination of controling some factors and averaging over others makes accurate quantitative research possible.

Most people make choices every day to do things that improve our health or safety in a probabilistic manner as a result of this kind of research:
· We wear sunscreen.
· We try and quit smoking.
· We lose weight.
· We have our cholesterol checked.
· We buy a fire extinguisher.
· We check the batteries in our smoke detector.
· We investigate the safety record of a model of automobile before we buy it.
· We investigate the probabilistic failure rate of our method of contraception.
· We (females) get mammograms after a certain age.
· We (men) get prostate screenings after a certain age.
· We might even eat oat bran.

Therefore, there is similar value in seeking a probabilistic understanding of bullet effectiveness to aid in ammo selection. Research in this area also has important implications for training, shot placement, and future bullet designs.

Michael Courtney
Link Posted: 12/23/2005 2:26:32 PM EDT
PAEBR: You seem to have a great affinity for picking apart everything like a shithouse layer.

You use the quicksilver method like a pro. Every time Dr Courtney replies to one of your questions, you quickly slid out from under the response and make some other wild accusation.

Perhaps you can list any actual credential you might possess?

Perhaps you can point out a short list of anything you ever had published? (bathroom walls don't count)

Other than rubbing your ego, what is it you actually contribute here???
Link Posted: 12/23/2005 2:44:24 PM EDT
Link Posted: 12/23/2005 2:50:50 PM EDT

Originally Posted By Lumpy196:


That was my take when I saw it on GlockTalk.
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