If hydrostatic shock were a fact??

[flytie]

Er chaps, I think the point is not linguistic is nature, rather centring on the phenomenon.

The word hydrostatic is indeed mis-applied, however so would any other word be unless we define the phenomenon we are talking about.

GH, you mean like the term that Rathcoombe uses?
Quote;

"Before I become too dogmatic and overstate the situation, let me concede that there may be some merit to the idea that hydrodynamic (not hydrostatic) impulse created by bullets which have a high kinetic energy and generally exhibit violent cavitation, can cause some secondary effects due to pressure on the nervous system or heart."



ft

 

[Ade 30-06]

Well spotted FT, I for one thought it was hydrostatic shock. I have learnt, yet again . HYDRODYNAMIC shock, yes I believe in the theory. Deer drop on the spot for different reasons, nervous system shots are a prime example. I have frequently shot deer from quartering away and I think they drop quickly due to the wind being taken away from them. I also believe that a bullet going through the correct area will cause a blood pressure surge that can knock out a deer causing it to drop. This phenonemom will not happen all the time, but is part of the variety of effects that a projectile will have on an animal.

One does concur with this judgement, phenomenon...yes.....reliable in all instances.......no. Too many variables.. Hmmmhmmmm where's ma'pipe n'baccy Mwtha !

 

[Grandhubert]

I'm not sure what you mean Flytie, The name of the phenomenon causing incapacitation to the deer I mean.

Until the nature of the phenomenon that kills the deer referred to above is known how can anyone say what phenomenon causes it?

In that context the nature of words "Hydrostatic" and "hydrodynamic" are irrelevant.

Specifically "hydrostatic" refers to the dynamics of fluids at rest, ie mainly gravitationally orientated, and hydrodynamics, when not taken to mean the study of fluid dynamics as a whole, is usually taken to mean the dynamics of fluid not at rest.

The misaaplication of the phrase "hydrostatic shock" is therefore a linguistic faux pax, at best peripheral to the issue at hand.

This might in fact be why I asked that the term be defined in my first post on the topic.

I took the OP intention to be what sort of bullet contruction tends to cause the effect we are describing rather than absolutely literally.

 

[flytie]

GH, If there is such a phenomenon, surely it is best to try and give a usable name to it, instead of an oxymoron. Granted it is a subject full of dispute, but there is sometimes an observed reaction to a shot which is out of proportion to what is normally seen.

To continue to use terminology which at best is confusing, and at worst just plain wrong, cannot contibute anything to the debate. At leat "Hydrodynamic impulse" is an accurate discription of some peoples theory and not an oxymoron.

ft

 

[Grandhubert]

I agree that using inaccurate terminology is not the way forward, I am merely interested in the phenomenon itself.

A case in point is the phrase you suggest, hydrodynamic impulse/shock could indeed be the name of the phenomenon, unless hydraulic shock proves to be better because, say it turns out the theory about the BP spike traveling up the carotid artery and causing a stroke is in fact correct.

This is why to my mind the probable physical cause of the incapacitation must first be reasonably put forward, so that links can be made to the bullet in any more than the most general sense.

A few thoughts that guide me in the discussion are these:

1. The body is not a bag of fluid; it is many, many small bags of fluid, the bags being of elastic and tough collagen membranes. A few organs are not fundamentally rubbery ( the brain, the liver, the spleen etc). A pressure wave would very rapidly be damped by this sort of tissue structure and not travel with significant force much past the wound site. I think this is why an animal shot in the arse with a very high velocity bullet does not immediately keel over dead.

2. The Lungs are especially tough and mostly made of air in a living animal. This makes them especially bad at propagating pressure, or any other, sort of wave.

3. Fluid is incompressible whereas the container of said fluid may deform under pressure. By this I mean that arteries and veins are stretchy and resilient, the further from the site of wave induction the weaker the force.

From the above I still think the BP spike to the brain causing stroke and unconsciousness, with death caused by massive loss of BP, is the most likely explanation for the phenomenon above.

I'm not sure what it should be called but can see that a higher velocity and greater frangibility would increase the chance of a wave of sufficient power and of sufficiently rapid propagation, so as defeat the artery stretch effect, affecting the brain through the carotid.

That make me think that quite a lot of it would be down to chance, because of factors involving the heart, the heartbeat, underlying health of the animal etc, that I don't know enough about to begin guess at.

Thank you for your thoughts by the way Flytie, it's a fascinating topic and I’ve learned a hell of a lot from the two threads I must say.

Regards,

A

 

[flytie]

Thank you for your thoughts by the way Flytie, it's a fascinating topic and I’ve learned a hell of a lot from the two threads I must say.

Regards,

A

A, I keep reading (and re-reading) all I can about this, I too am fascinated by it!

ft

My brain hurts!

 

[gitano]

There are PLENTY of terms used in the hunting/shooting community that are "technically" incorrect, yet are used and accepted widely. My favorite pet peeve (an intended oxymoronic phrase just for Mr. Rathcoombe's benefit) is "caliber" instead of cartridge or "chambering". I.E. What "caliber" is that rifle?" With the response being ".300 Winchester." No, that's the chambering or cartridge. The caliber is .308". I, however, do not have a little "hissy fit" every time I hear those terms mis-used. Neither do I accuse the users of spreading "pseudoscience babble".

While I am not particularly a proponent of the use of the term "hydrostatic shock", I'm not so "disturbed" by the use of "hydrostatic" or "shock" as Mr. Rathcoombe is, and I most vigorously disagree that it's use is "confusing" or that it is "pseudoscience babble". Mis-application of terms - something Mr. Rathcoombe is himself guilty of - isn't "pseudoscience bbble", it's simply error.

Second:

Shock, in the technical sense, indicates a mechanical wave travelling in excess of the inherent sound speed of the material;

In Mr. Rathcoombe's desire to demonstrate his superiority he instead demonstrates nicely the old adage that a little knowledge is a dangerous thing. While it is quite straight-forward to demonstrate that the blanket application of the above statement is stupid in the context of this discussion, (yeah, I mean stupid, not ignorant), let me instead use Mr. Rathcoombe's own words to illustrate the error, both logical and technical, of that statement.

After his "technical" tirade, Mr. Rathcoombe makes the following comment:

Before I become too dogmatic and overstate the situation, let me concede that there may be some merit to the idea that hydrodynamic (not hydrostatic) impulse created by bullets which have a high kinetic energy and generally exhibit violent cavitation, can cause some secondary effects due to pressure on the nervous system or heart."

(Too late on the "dogmatic", and I am prompted to quote Sir Willam Osler (1849 - 1919)

The greater the ignorance the greater the dogmatism.

Arrogance aside, here's the stake in his self-righteous "technical heart":

and generally exhibit violent cavitation

You can't have "cavitation", and not have a "shock wave" (a high-amplitude wave traveling faster than the speed of sound in the medium in which the wave travels). "Cavitation" is a technical term that describes one of the phenomena associated with a "shock wave". In a nutshell, it is the rending of the medium when a high-amplitude compression wave exceeds the speed of sound in the medium in which it travels.

The assumption that a "shock wave" (the "technical" shock wave of Mr. Rathcoombe's own assertions), can't occur in an animal is wrong. Mr. Rathcoombe's willingness to play 'fast and loose' with technical terms (or would a better description be "pseudoscience babble") is exceeded only by his willingness to "blow smoke". Either that, or he's profoundly ignorant of the anatomy of ANY animal. The fact of the matter is, there are MANY components of an animal's body that have neither the density of "water" NOR the speed of sound of water.

That's only the first of the errors of that statement. The second is that it "homogenizes" a very complex "system" (an animal) into a single uniform "form". That's convenient for Mr. Rathcoombe's pontifications, but it's wrong - both technically, and scientifically. That would be the same "technical" and "scientific" high horse from which Mr. Rathcoombe preaches. An animal is composed of a variety of "materials", some of which are non-compressable - like blood - and some of which are highly compressable - like air. As a compression wave, ANY compression wave, transitions from travelling in a non-compressible medium to a compressable medium, there is a tremendous conversion of energy to heat, AND if the direction of travel is from a non-compressable medium like blood to a compressable medium like air (in lungs), there WILL BE CAVITATION - AKA "rending".

Mr. Rathcoombe's "treatise" is rife with the likes of "casual" (or duplicitous or, using his own description, "pseudoscience babble") assumptions, flat out technical error, logical contradictions, and almost incomprehensible arrogance. The arrogance is all the more offensive because he is so consistently wrong in the pontifications he spews from his righteous high horse.

That said, Gallileo Gallilei (1564 - 1642) expressed well my opinion of Mr. Rathcoombe's tratise:

I have never met a man so ignorant that I couldn't learn something from him.

Paul

 

[Dalua]

You can't have "cavitation", and not have a "shock wave" (a high-amplitude wave traveling faster than the speed of sound in the medium in which the wave travels).

Where 'cavitation' is used to mean 'the formation of a cavity', it is difficult to see why not.

"Cavitation" is a technical term that describes one of the phenomena associated with a "shock wave".

That might well be true, but I must admit I have aways read the word in ballistic discussions as meaning 'the formation of a cavity'. That is perhaps an error on my part, but as a technical term, cavitation does have more than one meaning; including, I think, the phenomenon of bubbles seen around propellors on boats; this, I think, is related to localised low pressures in the water adjacent to the propellor.

I also keep wondering if it is disingenuous to describe blood as non-compressible when we are speaking of it contained in a large number of flexible, elastic structures inside an animal. I find it difficult to see how a 'shock-wave' could pass up blood in a flexible vessel (as opposed to in a rigid one) any significant distance as presumably, with forces acting equally in all directions in a fluid, the elasticity of the vessel's sides would rapidly and harmlessly dissipate the energy.

...thatAND if the direction of travel is from a non-compressable medium like blood to a compressable medium like air (in lungs), there WILL BE CAVITATION - AKA "rending".

Rending, forming a cavity, I suppose so. As you have pointed out, a light, fast bullet into a beast's chest does a good deal of rending. My inference from that would be that bits of bullet and rib showered in there are responsible for the swifty-terminal rending observed. Another theory of the cause is of interest but not, perhaps, necessary.

Mr. Rathcoombe's "treatise" is rife with the likes of "casual" (or duplicitous or, using his own description, "pseudoscience babble") assumptions, flat out technical error, logical contradictions, and almost incomprehensible arrogance. The arrogance is all the more offensive because he is so consistently wrong in the pontifications he spews from his righteous high horse.

I must express again my astonishment at the severity of your reaction to his essays, which seem to me both temperate and coherent. I quote Rathcoombe:

I will make a general statement which I will defend at length as we go along. Assuming that a bullet creates at least a 3/4 to 1 inch (19 to 25 mm) diameter hole through the vitals (a well placed shot), penetration is the more important of the two functions of a bullet for the big game hunter. A 3/4 inch (19 mm) hole which severs major arteries or passes through blood bearing vital organs will cause a rapid loss of blood pressure and will drop most targets within 50 yards. This is not to suggest that extreme cavitation will not cause an animal to succumb more rapidly. It could. However, bullets which cause extreme cavitation generally do not penetrate deeply and may not be suitable for some aspect angles due to the depth of penetration required to reach vital organs or the presence of interposing heavy bones. On the other hand, if only broadside body shots are taken, extreme cavitation may deliver the highest proportion of rapid kills.

...which seems to sum up the experience you have shared with us of the use of fast, frangible bullets in broadside shots, and also my experience with slower, heavier bullets.

So perhaps there is not so much to get excited about.

 

[flytie]

Interesting, as normal Dalua! I too have your take on what cavitation meant in wounding. Here are a few definitions;
http://www.google.co.uk/search?hl=e...n&sa=X&ei=B_y9TPP-BdjNjAfP3c2TAg&ved=0CBoQkAE

ft

 

[gitano]

I made a grave error in responding outside the context of the question posed in the original post. I sincerely regret having done so.

In my opinion, Muir has provided the most on-topic and appropriate response.

Dalua, I'll respond to your comments to my post using Private Mail.

Paul

 

[Dalua]

Dalua, I'll respond to your comments to my post using Private Mail.

My view is that further discussion on these matters would be more useful (if it is indeed useful at all!) in the public domain.
I am disinclined to enter into private correspondence on this matter as I feel I understand it poorly, and therefore the peer review to which public remarks are naturally exposed is invaluable.

 

[gitano]

OK.

Paul

 

[Grandhubert]

Good show, I also am rather interested in this topic and glad that it shall remain in the public domain.

 

[Ulfhere]

This thread is almost two years old, but since it is still active and my material is being impeached so vehemently I thought I would rebut.

Gitano states: "You can't have "cavitation", and not have a "shock wave"..."

This is an incorrect assertion. In fact, cavitation occurs very often in subsonic flows. It famously occurs on the trailing surface of submarine propellers. It is also the working mechanism for supercavitation, which is a phenomenon that, at least in its military applications, is always subsonic.

Gitano further asserts: "The assumption that a "shock wave" (the "technical" shock wave of Mr. Rathcoombe's own assertions), can't occur in an animal is wrong. Mr. Rathcoombe's willingness to play 'fast and loose' with technical terms (or would a better description be "pseudoscience babble") is exceeded only by his willingness to "blow smoke". Either that, or he's profoundly ignorant of the anatomy of ANY animal. The fact of the matter is, there are MANY components of an animal's body that have neither the density of "water" NOR the speed of sound of water."

What I stated is that living tissue has a sound speed similar to the sound speed of water. Actually it is slightly higher (reinforcing my point). I have amended my website in that section to reference a source that provides the sound speed of muscle and fatty tissue, the former being more than 1500 m/s. So, my statement that a shock wave will not occur in living tissue with any ordinary ballistic impact is valid.

If anyone finds any technical or editorial errors in my site, please feel free to bring them to my attention.

Regards, HTL

 

[Muir]

I think you're throwing punches after the arena has cleared.~Muir

 

[Vipa]

This thread is almost two years old, but since it is still active and my material is being impeached so vehemently I thought I would rebut.

Gitano states: "You can't have "cavitation", and not have a "shock wave"..."

This is an incorrect assertion. In fact, cavitation occurs very often in subsonic flows. It famously occurs on the trailing surface of submarine propellers. It is also the working mechanism for supercavitation, which is a phenomenon that, at least in its military applications, is always subsonic.

Gitano further asserts: "The assumption that a "shock wave" (the "technical" shock wave of Mr. Rathcoombe's own assertions), can't occur in an animal is wrong. Mr. Rathcoombe's willingness to play 'fast and loose' with technical terms (or would a better description be "pseudoscience babble") is exceeded only by his willingness to "blow smoke". Either that, or he's profoundly ignorant of the anatomy of ANY animal. The fact of the matter is, there are MANY components of an animal's body that have neither the density of "water" NOR the speed of sound of water."

What I stated is that living tissue has a sound speed similar to the sound speed of water. Actually it is slightly higher (reinforcing my point). I have amended my website in that section to reference a source that provides the sound speed of muscle and fatty tissue, the former being more than 1500 m/s. So, my statement that a shock wave will not occur in living tissue with any ordinary ballistic impact is valid.

If anyone finds any technical or editorial errors in my site, please feel free to bring them to my attention.

Regards, HTL

This is subject matter that interests me greatly and whilst it is an old thread I do have a question..

When you see the super slow motion film of projectiles hitting ballistic jelly... if it's not a shock wave, what is it that causes the the all that movement and distortion as the projectile passes through? Example at 1m 53s

 

[Ulfhere]

Its a pressure wave created by the dynamic pressure of the projectile's passage. The matter regarding the use of the word "shock" is mostly about semantics, but I will add this: even if it truly were a shock wave, it would not cause any more damage. We hear the word shock used a lot in various contexts and we associate it with an unusual level of trauma or damage. But in the case of ballistic impacts, the only thing that is essential is the kinematics, which describe the pressure created, its magnitude and extent. This governs the event and whether or not that wave is traveling at a supersonic rate locally is not relevant to the discussion in any significant respect. Supersonic conditions matter in terms of drag for aircraft and to a far lesser extent to bullets, but not in this regime. In the penetration mechanics of shaped charges the supersonic penetration is what makes them so effective, but that is because the jet is made of weaker material than the target armor and so it needs that in order to side step the strength of the material (the problem becomes a simple matter of Bernoulli's equation for the flow of two fluids). In the case of bullets, you don't get this relationship between the projectile and the target. That might be true for bullet vs bone, but you would have to be penetrating at an unbelievably high speed (not sure what the sound speed for bone is, but its surely a lot higher than for soft tissue).

Regards, HTL

 

[Vipa]

Its a pressure wave created by the dynamic pressure of the projectile's passage. The matter regarding the use of the word "shock" is mostly about semantics, but I will add this: even if it truly were a shock wave, it would not cause any more damage. We hear the word shock used a lot in various contexts and we associate it with an unusual level of trauma or damage. But in the case of ballistic impacts, the only thing that is essential is the kinematics, which describe the pressure created, its magnitude and extent. This governs the event and whether or not that wave is traveling at a supersonic rate locally is not relevant to the discussion in any significant respect. Supersonic conditions matter in terms of drag for aircraft and to a far lesser extent to bullets, but not in this regime. In the penetration mechanics of shaped charges the supersonic penetration is what makes them so effective, but that is because the jet is made of weaker material than the target armor and so it needs that in order to side step the strength of the material (the problem becomes a simple matter of Bernoulli's equation for the flow of two fluids). In the case of bullets, you don't get this relationship between the projectile and the target. That might be true for bullet vs bone, but you would have to be penetrating at an unbelievably high speed (not sure what the sound speed for bone is, but its surely a lot higher than for soft tissue).

Regards, HTL

Ok... I get that (mostly! ) so the question is then, is the debate as to whether hydrostatic shock is real or not just a terminology issue? The dynamic pressure wave appears to produce quite violent cavitation in the jelly, would this wave and subsequent cavitation be strong enough to rupture vital organs or even break bones as has been suggested?

 

[Brithunter]

Just watched the video and had to laugh. Firstly they compare a pitted barrel with what looks like an almost new one. They try to pass the pitting off as copper fouling. Right there I knew that as they have to resort to this deception the rest i going to be pure B/S and spin.

Now looking at there new super dooper bullets what is ee is a blatant copy of the GS bullet.

As for the shock and the various theories I really don't know but I do know that get it wrong and you end up with lots of jellified meat.

 

[Vipa]

Just watched the video and had to laugh. Firstly they compare a pitted barrel with what looks like an almost new one. They try to pass the pitting off as copper fouling. Right there I knew that as they have to resort to this deception the rest i going to be pure B/S and spin.

Now looking at there new super dooper bullets what is ee is a blatant copy of the GS bullet.

As for the shock and the various theories I really don't know but I do know that get it wrong and you end up with lots of jellified meat.

I know... but it was the first vid I came accross with decent HS filming in it... just ignore the other rubbish