.40 Caliber Pressure Wave Effects

[Michael Courtney]

.40 Caliber Pressure Wave Effects

We had an opportunity this weekend to perform an informal field necropsy on a 180 lb 7 pt buck shot with a 135 Grain .40 caliber Nosler JHP at approximately 1350 FPS impact velocity. Though fired from a muzzleloader, this impact velocity closely approximates the impact velocity of the same bullet fired from a .40 S&W. This load produces one of the larger pressure waves available from JHP ammo in 9mm, .40S&W, .45 ACP, or .357 Sig. This buck was shot during a special youth-only hunt, and the young hunter was gracious enough to allow a couple of scientists access to his deer.

The effects of the pressure wave on tissue were impressive. The bullet entered just in front of the third rib (counting from the back) on the left side, pulverized a large (1.5” diameter) on the inside of the rib cage and in the liver, entered the left lung producing a large (1” diameter) pulverized region, entered the right lung producing a pulverized region that gradually shrank in size to the recovered diameter of the bullet (0.58”), exited the rib cage just in front of the 11th rib (counting from the back) and was recovered in the muscles of the right shoulder. The direction of the wound agrees with the account of the shot that the buck was mostly broadside, but angled slightly away with his head down grazing.

According to the PCC-only view of handgun bullet wounding (espoused by Fackler/IWBA adherents), the expected wound channel (which assumes crushing is the only mechanism) should be roughly cylindrical in shape, and have a diameter roughly equal to the recovered diameter of the bullet. The volume of this expected wound channel is widely known as the permanent crush cavity (PCC) and given by the frontal area of the recovered bullet times the penetration depth (12”). This gives an expected wound volume of 3.17 cubic inches.

What we actually observed is a truncated cone region of pulverized tissue with a diameter of 1.5” on the entrance side, and gradually narrowing to 0.58” on the exit side of the rib cage. The actual volume of this truncated cone of pulverized tissue is 12.18 cubic inches, or nearly 4 times the volume predicted by the PCC-only view of wounding via handgun bullets.

In addition, we observed a region of severe to moderate hemorrhaging along the wound channel that was 5” in diameter at entrance, narrowed to roughly 3” in diameter at the medial surface of the left lung and gradually shrank in size to merge with the bullet diameter where the bullet exited the rib cage. This region of hemorrhaging has an approximately truncated cone shape with a volume of 119.3 cubic inches.

We believe that the pressure wave is responsible for this hemorrhaging, though we cannot rule out the temporary stretch cavity for some regions. However, the 5” diameter of hemorrhaging of the muscular tissue surrounding the entrance wound is much larger than the expected TSC at this point. This is the effect that hunters associate with high-velocity rifle bullet wounds and refer to as bloodshot meat. Since the pressure wave is more strongly directed backward than the TSC, it makes sense that this hemorrhaging is due to the pressure wave.

We also observed mild hemorrhaging along the abdominal walls and rear rib cage on the right side. This is the area directly opposite from the entrance wound, but considerably rearward from the point where the bullet exited the rib cage. Thus this region was out of reach of both the permanent crush cavity and the temporary stretch cavity, and it seems that the most likely cause of the hemorrhaging was the pressure wave.

Inspecting the site of the shooting revealed that the deer ran 54 yards (straight line distance) from where it was shot to the point where the carcass was recovered. This is in good agreement with our empirical models which predict the average drop distance from the IWBA-type PCC volume and the peak pressure wave magnitude. In spite of the absence of an exit wound, there was an extremely profuse blood trail spread along the path the deer ran.

The wounds we observed for the 135 grain Nosler JHP are very similar to those observed in earlier studies with the 115 grain Triton Quik-Shok at .357 Sig velocities. In both cases, there is substantial tissue damage and destruction beyond the tissue crushed directly by the projectile. These two loads generate comparable pressure waves.

The tissue damage we observed from the 135 grain Nosler JHP is markedly different from that which we have observed on earlier occasions with lower pressure wave bullets such as the 147 grain Winchester 9mm bullet at 9mm velocity levels. The tissue damage due to the 147 grain 9mm bullet is very much in accordance with the PCC-only view espoused by Fackler/IWBA adherents: a nearly cylindrical region of crushed tissue with a diameter well approximated by the expanded diameter of the bullet. There is little tissue damage beyond the tissue crushed directly by the bullet.

This same 135 grain Nosler JHP bullet is also available in 10mm. We estimate the pressure wave in the 10mm Double Tap loading to be 50% larger than the pressure wave generated at 40 S&W velocities. Interesting. The performance potential of this bullet is almost enough to make me trade in my .357 Sig.

Michael Courtney

 

[mete]

Thanks Michael, keep doing the studies , we'll learn a few things !

 

[Shear_stress]

Very interesting. With all the speculation about wounding mechanisms flying around, it's great to have some empirical evidence.

It's not too surprising that a pressure wave would cause hemorraging in a region surrounding the wound. Tissue is a relatively dense, roughly incompressible medium that will amply transmit pressure pulses that may be more than enough to burst capillaries in a fairly wide radius around the wound. Add to that the body's propensity for inflammatory response (especially at an elevated heart rate), and you've got a big mess in there.

Before anyone runs out and tries to compare this to a wound caused by a high-powered rifle, remember that there is a lot more velocity at work there. In fact, the sudden rise and drop in pressure in the wound track of a rifle bullet may be enough to cause cavitation in the tissue (in addition to tissue stretching and a big honkin' pressure wave). Yuck.

Keep up the good work!

 

[P95Carry]

Most detailed and useful report Michael - thank you

 

[LightningJoe]

Thanks for a little light. It's dark in here.

 

[JohnKSa]

The jello junkies are going to string you up--sho' nuff...

 

[ghost squire]

http://www.firearmstactical.com/images/Wound Profiles/45 ACP WW STHP.jpg

http://www.firearmstactical.com/images/Wound Profiles/45ACP 230gr FMJ.jpg

Doesn't look cylindrical to me! From a Facklerite/IWBA site.

I have a question, did the bullet go through the heart?

Also keep in mind that flesh that is hemmoraghed by a bullets energy outside of the crush cavity takes several seconds to even start bleeding.

I'm not trying to detract from your work, just put it in perspective. If the bullet pulverized the heart without actually touching it, then I am very suprised and will have to rethink my stance on the entire matter of wound ballistics.

 

[Michael Courtney]

http://www.firearmstactical.com/images/Wound Profiles/45 ACP WW STHP.jpg

http://www.firearmstactical.com/images/Wound Profiles/45ACP 230gr FMJ.jpg

Doesn't look cylindrical to me! From a Facklerite/IWBA site.

The diagrams you reference do indeed show the permanent crush cavity to be cylindrical. The non-cylindrical outer regions represent the temporary stretch cavity (TSC). Fackler and the IWBA folks have asserted adamantly on many occasions that the TSC does not cause significant wounding in handgun bullets.

We believe that the pressure wave is more important than the TSC in incapacitation via handgun bullets, but since there is a large correlation between the two, it is hard to be absolutely certain at this time. However, from our observations, we do have a high level of certainty that there is some effect other than the PCC that is responsible for a great deal of tissue damage. Our observations also indicate that at least some of this damage is more likely due to the pressure wave than the TSC, because we observe some wounding in tissue beyond the reach of the TSC.

In any event, the observation of a handgun bullet at 1350 FPS creating a truncated cone of pulverized tissue with a volume nearly 4 times the PCC volume is contrary to what one would have expected from the IWBA opinion that the permanent crush cavity is the most important and only reliable predictor of handgun bullet effectiveness. In contrast, it is quite consistent with emperical models based on the Strasbourg Goat Tests and/or Marshall and Sanow OSS data which suggest that a model including both the PCC and the pressure wave magnitude (or TSC) can predict relative handgun bullet effectiveness.

I have a question, did the bullet go through the heart? [/QUOTE] No. Michael Courtney

 

[ghost squire]

Fackler and the IWBA folks have asserted adamantly on many occasions that the TSC does not cause significant wounding in handgun bullets.

And they appear to be correct in the context that they say that in.

I very seriously doubt that destruction of random tissue is going to aid significantly in stopping an attacker in a self defense situation. Now, the bullet did go through both lungs, but if I am not mistaken, any significant hole in a lung is going to deflate it and make it stop working. I might be wrong here... Therefore the "pressure wave" and TSC didn't appear to help all that much here.

Now if that particular cartridge has the ability to destroy the heart purely by TSC or "pressure wave", then I am very impressed, and the IWBA would certainly have to take notice.

But according to my research a minimum velocity of 1500 FPS is required to do that.

Could you please define what the difference between a pressure wave and the TSC is? I haven't heard that term before in terminal ballistics speak.

 

[Shawn Dodson]

The diagrams you reference do indeed show the permanent crush cavity to be cylindrical.

Yes indeed, they are incorrect. Permanent cavity diameter is larger at the beginning of the wound track and decreases in diameter as velocity decreases.

The wound ballistics terminology used by Dr. Courtney is non-standard, and thus can be confusing. IMO, there's no need to reinvent the wheel.

The term "PCC" is misleading. Permanent tissue damage (permanent wound) is not limited to the crush mechanism.

"TSC" = "stretch" is redundant. It's redundant because the tissues stretch and rebound - hence "temporary." "Temporary cavity (TC)" is the standard term.

Not sure what is meant by the term "pressure wave."

 

[Michael Courtney]

Yes indeed, they are incorrect. Permanent cavity diameter is larger at the beginning of the wound track and decreases in diameter as velocity decreases.

Is there prior work showing that a .40 Caliber bullet can produce a permanent cavity that is 1.5" in diameter near the entrance and shrinks to 0.58" in diameter near the end? It was my impression that the IWBA idea is that the bullet has to physically impact the tissue to cause damage, so the damage is limited to the actual diameter of the bullet at that point in the wound tract. Correct me if I am wrong, but doesn't _Handgun Wounding Factors and Effectiveness_ say,

"The tissue disruption caused by a handgun bullet is limited to two mechanisms. The first, or crush mechanism is the hole the bullet makes passing through the tissue. The second, or stretch mechanism, is the temporary cavity formed by the tissues being driven outward in a radial direction away from the path of the bullet. Of the two, the crush mechanism, the result of permanent cavity and penetration, is the ONLY handgun wounding mechanism which damages tissue."

So, the IWBA viewpoint seems to be that the only way for a handgun bullet to damage tissue is to crush it by direct contact. Thus, the diameter of the permanent cavity cannot exceed the diameter of the bullet as it passes a given point along the wound channel. If the maximum diameter of the bullet exceeds the final recovered diameter because the bullet erodes a bit, then the permanent cavity diameter can also decrease. But this isn't a very large difference, and if I recall correctly, it is a common and accepted practice for JHP handgun bullets to estimate the permanent cavity volume as the recovered frontal area of the bullet times the penetration depth.

The wound ballistics terminology used by Dr. Courtney is non-standard, and thus can be confusing. IMO, there's no need to reinvent the wheel.

The term "PCC" is misleading.

I picked up the term "Permanent Crush Cavity" at the Firearmstactical.com web site.

http://www.firearmstactical.com/briefs10.htm

Permanent tissue damage (permanent wound) is not limited to the crush mechanism.

This seems to contradict the excerpt from _Handgun Wounding Factors and Effectiveness_ quoted above.

"TSC" = "stretch" is redundant. It's redundant because the tissues stretch and rebound - hence "temporary." "Temporary cavity (TC)" is the standard term.

Once again, I found the term in use at the Firearmstactical.com web site.

http://www.firearmstactical.com/tacticalbriefs/volume4/number1/article412.htm
http://www.firearmstactical.com/tacticalbriefs/volume4/number1/article414.htm

Let's face it, the firearmstactical site pretty uniformly ascribes the "crush" mechanism to the "Permanent Cavity" thus calling it the "Permanent Crush Cavity" is simply addng the mechanism to the name. Likewise the stretch mechanism is uniformly assigned to the "Temporary Cavity" thus "Temporary Stretch Cavity" is simply adding the mechanism to the name. The terms "Permanent Crush Cavity" and "Temporary Stretch Cavity" are standard and commonly used substitutes for "Permanent Cavity" and "Temporary Cavity" and everyone in the field knows what one means whichever term is used.

Not sure what is meant by the term "pressure wave."

Any time there is a dynamic force applied to a viscous or visco-elastic medium, a pressure wave is created. From a physics viewpoint, this is the pressure supplying the force which expands and decelerates the bullet. The wave propagates outward in all directions from the point of contact between the visco-elastic meduim and the bullet.

The scientific debate revolves around whether the pressure wave contributes to wounding and incapacitation. The Fackler/IWBA opinion is that neither the pressure wave nor the temporary stretch cavity reliably contribute to wounding or incapacitation via handgun bullets.

The pressure wave magnitude can be accurately predicted from applying 1st year college Physics to standard parameters measured from shooting bullets into ballistic gelatin. These kind of predictions can be confirmed by instrumenting ballistic gelatin with a high-speed PZT-based or strain gage-based pressure transducer connected to a high-speed data acqusition system such as a digital oscilloscope. This instrumentation is very similar to that used to measure the transient pressure impulse present inside a gun chamber and barrel.

A more widely accessible method to get a rougher view of a ballistic pressure wave is to shoot a block of ballistic gelatin sitting on a force plate (similar to a digital scale with a very fast response). The force plate measures the instantaneous downward force of the gelatin block. The bullet creates a pressure wave in the block. The pressure wave radiates outward from the bullet path in all directions. When the pressure wave hits the interface between the block and the plate, the pressure wave exerts a downward force on the plate which can be recorded with a digitial oscilloscope or other analog to digital converter.

A more visual (but less scientific) manner to view the pressure wave is to view it's effect when shooting fruit. In short, when you shoot a watermelon, it explodes due to the outward force of the pressure wave.

Michael Courtney

 

[RecoilRob]

I have been following this thread and it has me wondering a couple of things.

1350fps for a sabot muzzle loader is really, really slow. As you stated the velocity as 'approximate' is there a possibility that it could have been higher? Was the gun and load ever run over a chrono and what was the gun/load combo?

1350fps is about the max muzzle velocity attainable in the .40 and will be substantially higher than any reasonable impact velocity short of a contact wound. Would 100fps reduce the wounding effect to what the 'books' say is normal for the round?

Finally, not being up on my Deer Anatomy, is deer flesh the same as human when comparing wounds?

Not saying that what you observed isn't accurate. I believe every word but also believe what Fackler and company have produced over the years and am just searching for a reasonable explanation to allow both to exist in harmony.

 

[Michael Courtney]

I have been following this thread and it has me wondering a couple of things.

1350fps for a sabot muzzle loader is really, really slow. As you stated the velocity as 'approximate' is there a possibility that it could have been higher? Was the gun and load ever run over a chrono and what was the gun/load combo?

The impact velocity was estimated from the muzzle velocity (1800 FPS), the ballistic coefficient (0.093), and the measured distance from muzzle to impact (65 yards). I have no reason to doubt the reported muzzle or impact velocity, but being a scientist, I intend to double check these. I am in possession of the gun, powder, and identical samples of bullet and sabot, and I intend to double check the muzzle velocity at the stated powder charge. I'd rather not list the powder charge, because each gun/powder/load combination is a law unto itself and the chronograph gives a much more accurate velocity than can be inferred from the powder charge. However, I've seen comparable powder charges in other muzzleloaders give comparable and even lower velocities. I also intend to do time of flight measurements to confirm the published ballistic coefficient.

1350fps is about the max muzzle velocity attainable in the .40 and will be substantially higher than any reasonable impact velocity short of a contact wound. Would 100fps reduce the wounding effect to what the 'books' say is normal for the round?

Double Tap lists this bullet at 1375 FPS from a 4.0" barrel and 1420 FPS from a 4.5" barrel in their .40 S&W load. Most gun fights occur at ranges where the impact velocity will still be at or above 1350 FPS. Even at a muzzle velocity of 1375 FPS, the impact velocity doesn't drop to 1250 FPS until beyond 20 yards. There aren't many gun fights at this range.

Finally, not being up on my Deer Anatomy, is deer flesh the same as human when comparing wounds?

As far as we can tell, it is comparable. 10% Ballistic Gelatin accurately predicts penetration depths, bullet expansion, and retained mass in both humans and deer. In cases where we have directly observed deer wounding and detailed descriptions are available for the same bullet in humans, our observations in deer agree with the descriptions in humans.

Not saying that what you observed isn't accurate. I believe every word but also believe what Fackler and company have produced over the years and am just searching for a reasonable explanation to allow both to exist in harmony.

There aren't many JHP handgun loads that produce pressure wave levels of this magnitude. I don't know how many "Fackler and company" have looked at, but I haven't found any detailed descriptions of wounding caused by this bullet.

Michael Courtney

 

[RyanM]

According to my calculations (based on lines of best-fit, based on data exclusively from "Facklerite" sources), a 135 gr bullet at 1350 fps which expands to .58" will crush an average diameter of .52", have a maximum temporary cavity of 3.1", and the resulting wound will have an average diameter of about .86" due to the temporary cavity's stretching. It does sound like the amount of damage you describe is easily explained by the temporary cavity, particularly because my data is based on pig buttock and thigh muscle, which is substantialy stronger than lung tissue.

The hemmoraging in a 5" area is easily explained by blunt trauma. Blunt trauma and tissue stretching are the mechanisms through which the temporary cavity injures. Naturally, the amount of bruising (in the form of bloodshot meat, before the blood clots and darkens) will extend beyond the temporary cavity. If you strike living soft tissues with a hammer, the bruise will extend beyond the tissue directly contacted by the hammer, and beyond the extent to which tissue is displaced by the blow.

 

[Michael Courtney]

According to my calculations (based on lines of best-fit, based on data exclusively from "Facklerite" sources), a 135 gr bullet at 1350 fps which expands to .58" will crush an average diameter of .52", have a maximum temporary cavity of 3.1", and the resulting wound will have an average diameter of about .86" due to the temporary cavity's stretching. It does sound like the amount of damage you describe is easily explained by the temporary cavity, particularly because my data is based on pig buttock and thigh muscle, which is substantialy stronger than lung tissue.

Would you be kind enough to cite the specific "Facklerite" sources to which you refer. I have been under the impression that the Facker/IWBA viewpoint is that the crush mechanism is the only handgun wounding mechanism which damages tissue. An oft cited reference to support this assertion is

From _Handgun Wounding Factors and Effectiveness_

"The tissue disruption caused by a handgun bullet is limited to two mechanisms. The first, or crush mechanism is the hole the bullet makes passing through the tissue. The second, or stretch mechanism, is the temporary cavity formed by the tissues being driven outward in a radial direction away from the path of the bullet. Of the two, the crush mechanism, the result of permanent cavity and penetration, is the ONLY handgun wounding mechanism which damages tissue."

If this position has been retracted (as it seems it must have from your opening paragraph), it is an interesting development that should be more widely communicated.

The hemmoraging in a 5" area is easily explained by blunt trauma. Blunt trauma and tissue stretching are the mechanisms through which the temporary cavity injures. Naturally, the amount of bruising (in the form of bloodshot meat, before the blood clots and darkens) will extend beyond the temporary cavity. If you strike living soft tissues with a hammer, the bruise will extend beyond the tissue directly contacted by the hammer, and beyond the extent to which tissue is displaced by the blow.

And how do blunt force trauma mechanisms damage tissue beyond that which is contacted directly? The force is transmitted through the tissue via a pressure wave.

Michael Courtney

 

[ghost squire]

I never interpreted what Fackler and his followers said to exclude temporary cavity as a wounding mechanism. Although that specific document does say that exact thing, which confuses me. What I always thought it meant is that while some cartridges can create significant permanent tissue damage outside of the direct path of the bullet, typical service cartridges cannot do this reliably through thick layers of clothing and after passing through say an arm, then the sternum which guards the heart, and then after an inch or two of flesh that is in front of the heart.

At 1500 FPS or higher I certainly expect the bullet to do this, and considering that the muzzle velocity was 1800 FPS and the animal shot at 65 yards, is it at all possible that you underestimated the impact velocity? Just asking

I will leave this up to the experts such as Shawn Dawdson though.

And until someone takes a human sternum, puts it in front of a deer and dresses that deer in a leather jacket and puts a human arm in front of that, maybe we won't know!

 

[RyanM]

I meant sources of plain, raw data. My equation for determining amount of stretching/tearing due to temporary cavitation was derived from both my temporary cavity equation, and from Fackler's paper "A reconsideration of the Wounding Mechanism of Very High Velocity Projectiles - Importance of Projectile Shape."

And what evidence do you have that it is the "pressure wave" that causes bruising, as opposed to stress transmitted via tissue compression?

 

[Michael Courtney]

And what evidence do you have that it is the "pressure wave" that causes bruising, as opposed to stress transmitted via tissue compression?

None. I don't believe there is an important distinction.

Biomechanics does not distinguish between pressure and stress in visco-elastic media such as living tissue. Pressure is force per unit area in a fluid (viscous) medium. Stress is force per unit area in a solid (elastic) medium. The concepts blur in media such as tissue that have both viscous and elastic properties. If one prefers to label the mechanism I am describing as a "stress wave" (transmitted by tissue compression) rather than a pressure wave, we would be describing the same thing by different terminology. The point is that the pressure/stress wave is capable of transmitting a force throughout the medium.

Michael Courtney

 

[Michael Courtney]

I meant sources of plain, raw data. My equation for determining amount of stretching/tearing due to temporary cavitation was derived from both my temporary cavity equation, and from Fackler's paper "A reconsideration of the Wounding Mechanism of Very High Velocity Projectiles - Importance of Projectile Shape."

Very nice and interesting. Care to share the data you've harvested and your resulting model? This should probably be published or at least distributed privately to interested parties. (Lest I be tempted to repeat the work independently and publish my own empirical model.)


Michael Courtney

 

[Michael Courtney]

At 1500 FPS or higher I certainly expect the bullet to do this, and considering that the muzzle velocity was 1800 FPS and the animal shot at 65 yards, is it at all possible that you underestimated the impact velocity? Just asking

I plan to verify this as described above. Nosler gives the bullet a BC of 0.093. The low BC is responsible for our estimate of an impact velocity of 1350 FPS. Nosler's BC is consistent with the shape of the bullet and the sectional density. If the BC is really higher then Nosler claims, it is possible that our estimated impact velocity is too low. On the other hand, Nosler is usually pretty accurate in their reported BC's. I'll be sure to report back here if our estimate of the impact velocity needs to be revised.

Michael Courtney

 

[Shear_stress]

I am curious how you define "temporary cavitation". Cavitation is caused when a sudden pressure drop forces a fluid to boil at a lower temperature than at atmospheric pressure and/or forces the gases dissolved in a fluid out of solution. It is a transient phenomenon that can cause permanent destruction of tissue.

That said, as far as my limited knowledge of ballistics goes, most handgun bullets do not travel fast enough to make cavitation a dominent wounding mechanism. I could be wrong.

Edited to add: though wound ballistics is not my area of expertise, I can clarify some of the terminology used in this discussion. Pressure and stress share the same units units of force per area, but are not treated the same in continuum mechanics. Typically, pressures are seen as exterior loads that transmit a "surface force", while stress distribution is what is considered inside a body. When we talk about the interior of a body, we usually consider stress, not force or pressure. Also, if we are talking about compressible flow, we can start referring to pressure waves as "shock" waves.

 

[Michael Courtney]

Pressure and stress share the same units units of force per area, but are not treated the same in continuum mechanics.

What you write is correct for solids, but stress is a very murky concept for visco-elastic media, and the concept of stress blends with the concept of pressure. I prefer to use the term pressure, because the wave moves outward in all directions as the medium does not support the kind of directionality suggested by a stress tensor.

Typically, pressures are seen as exterior loads that transmit a "surface force", while stress distribution is what is considered inside a body.

Defining the stress tensor makes sense and is manageable and tractable only in solids. In visco-elastic media pressures of this magnitude behave as pressures (rather than stress) in that the pressure is the same in all directions and you cannot define a stress tensor.

When we talk about the interior of a body, we usually consider stress, not force or pressure. Also, if we are talking about compressible flow, we can start referring to pressure waves as "shock" waves.

In the regions where the visco-elastic medium is behaving more like a fluid (not supporting a shear), it is more appropriate to consider pressure rather than stress. Calling the wave a "shock" wave has a lot of negative baggage in the field of terminal ballistics, so I have avoided this designation.

Michael Courtney

 

[Shear_stress]

The terminology used in continuum mechanics are derived independent of the material.

If the pressure is the same in all directions, you definately can define a stress tensor. This is simply the case when your three principle stresses are equal. What you can't define is a principle direction, and that is only because you have an infinite number of them at that point within the body.

Also, pressure is equal in all directions in hydrostatics, but is not the case when you have a moving pressure wave.

 

[Michael Courtney]

Also, pressure is equal in all directions in hydrostatics, but is not the case when you have a moving pressure wave.

It is possible to have a pressure wave that does not move equally in all directions, but we believe that the pressure wave radiates outward nearly equally in all directions for most bullet designs. One of the questions we hope to investigate is whether an anisotropic pressure wave would enhance wounding or incapacitation by focussing the energy of the wave in preferred directions like a directional gain antenna focusses an RF wave in preferred directions.

Michael Courtney

 

[Michael Courtney]

Also, pressure is equal in all directions in hydrostatics, but is not the case when you have a moving pressure wave.

It is possible to have a pressure wave that does not move equally in all directions, but we believe that the pressure wave radiates outward nearly equally in all directions for most bullet designs. One of the questions we hope to investigate is whether an anisotropic pressure wave would enhance wounding or incapacitation by focussing the energy of the wave in preferred directions like a directional gain antenna focusses an RF wave in preferred directions.

Michael Courtney