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How does "hydrostatic shock" propagate in an organ full of air?

Angus,

That's the first time I've ever heard that definition of "hydrostatic shock." The standard definition (or at least the only one I've heard of) involve the hydraulic compression of blood through the circulatory system. Where did you hear it?

In armor training. They explained for a sabot round to work correctly it had to leave the Or exit the turret. Thus sucking the crewmembers out with it. The web sight terminal ballistics research also discusses trauma based on velocity. I think smokepoles point is also valid in that the lungfield will be in a varying degree of susceptibility depending on its state of inflation upon impact. The other thing to consider in ruminants is the rumen which predominantly occupies the left abdomen and is basically inert sack of ingesta, this makes almost impervious to shock in that area.

I was going to mention this John -- his "long range" kill of a nice bull with the 270 when earlier he was fairly clear about the much more appropriate 30 cal to mediums for elk. This is not a criticism of CB at all as I have not found him dogmatic in his writing and opinions though you could easily infer those if they were not clearly stated, and he is also apparently pretty good company.

"Hydrostatic shock" is a nonsense term invented by non-ballisticians on the internet and has no credible definition in actual wound ballistics. I have never heard or read any such definition as the one you have posted, and I've been deeply involved in the wound ballistics community for nearly 20 years. Furthermore, how one could use a term that quite literally means "liquid" to describe a fictional event such as you describe (i.e., the sucking-out of a tank's crew by the drop in air pressure created by the exit of a high-velocity projectile) is beyond me. Water is liquid, air is gas. Hydraulics (the physics of liquids) do not translate over to the behavior of gases such as air.

When the International Wound Ballistics Association was still extant, several peer-reviewed papers were published in its journal that debunked "hydrostatic shock" as a nonsense term. Now there is such a thing as hydraulic shock, which is what JB described in his earlier post today, and which is essentially the propagation of a physical shock wave through a liquid medium that may cause remote injury. What we are describing then, is a physical shock wave through a liquid medium such as water, blood, or a liquid-filled organ such as the brain, liver, spleen, or urinary bladder. Studying the physics of shock waves teaches us that the energy of the wave diminishes geometrically with distance, so instances of remote injury from a missile (bullet) injury are uncommon at best.

DO NOT confuse the shock wave being discussed here with physiological shock. I note that Wikipedia's article on "hydrostatic shock" makes this error, mixing and conflating physiological shock (reduction or loss of blood pressure in response to a specific type of injury to the body) with the physics of shock waves. Please don't anyone quote any of the confused drivel from that Wikipedia article in this thread.




I think Isaac Newton would argue quite convincingly to the contrary.



I think perhaps you should.

Perhaps this admittedly questionable analogy is at least partially germane to the discussion with providing a mental picture of what "hydrostatic shock" might look like if it exists. I preface it with admitting no personal experience in stopping dangerous game nor am I claiming some degree of hydrostatic shock is even a stopping factor in and of itself as the body mass of the game has to be a big factor I suspect in mitigating its effect. Also, the temperament of the creature at the moment of the hit makes a difference in the immediate reaction to the hit. But I have watched what may be varying degrees of it in many ungulates expiring from solid chest hits over the years

Consider a big watermelon hit dead center at fifty yards with, say, a fast 30 and then with 22 LR to give extremes in bullet weight, frontal area, velocity, and energy and their effect pursuant to illustrating the point of the concept. And that a bigger, faster bullet of right design, equally well-place (controllability), trumps the lesser all day long in its effect. But with so many variables in hunting big game (not to mention you can never shoot the same animal twice under the same conditions) it's difficult to isolate to just the effects of a different caliber cartridge with the same bullet design.

A watermelon is ~ 90% + water. Water is not very compressible. We all can visualize the explosion of chunks of melon and the red mist in the air at the hit from the 30. The 22 hit depending on the size and weight of the melon might not even be discernible other than the slight melon wobble as it bored through and out.

Note: HS, if it exists, is not a ubiquitous factor -- Phil's killing the brown bear with a 9mm handgun at close range involved very little HS as far as I can imagine but provided enough leakage due to good bullet placement and penetration in an animal without an apparent "vengeful turn of mind" at that moment. Similarly, the 22 can be very lethal but we are talking of the effect on a time continuum, a very short one being optimim. The Masai with noted precision poke a hole in the carotid artery of their donor beast with a sharp stick to obtain blood for one of their culinary staples, and that animal would soon go to a forever sleep were it not for soon-applied pressure and a daub of mud over the big pounding vessel. There is certainly no HS there but it would be a quickly lethal wound being one of the larger pipes in the cardiovascular system..

A mammals percentage of water content is on the order of 70 to 60% on the conservative end with, of course, different tissue types and densities as opposed to the homogenous nature of a melon. The significant difference in total body water of mammals of course reduces the effect and the amount of air in the lungs should they be hit reduces it further yet. And as mentioned there are many other variables that enter in with a very mobile, aware mammal and certainly a dangerous one. A supremely important factor is bullet weight and design. Yet, while the melon scenario is an imperfect model, I have to believe it illustrates "some" of what I've seen in the reactions of many head of big game.

The point being, while there is rarely a consensus on the specifics of these matters, there are groups of cartridge/bullet combinations that over time and many experiences have shown themselves to be appropriate for different classes (size and temperament mainly) of game due to their effectiveness in quickly killing or even immediately stopping big game.

But I am pretty sure everyone here knew all of this already but it gave me something to reflect on again this morning. 😉

And I agree with the confusion of "hydrostatic shock" with "hydraulic shock" which I just exacerbated. Please consider the latter to be what I am referring to in the post above.

Doc,

I mentioned the common, nonsense definition of "hydrostatic shock" primarily to find out what Angus meant. You're absolutely right, it doesn't mean anything, but was a term promoted by many people during the early days of very high velocity cartridges, one of the biggest promoters being Roy Weatherby. As some people have pointed out in the past, even the term "hydrostatic" doesn't apply, as there's nothing static about it.

Roy Weatherby promoted hydrostatic shock with very high velocity bullets as THE answer to killing power. According to Weatherby, arteries and veins acted like brake lines, transmitting the impact of the bullet to the brain, killing animals no matter where the bullet landed. But he first formulated this theory (or followed the lead of other proponents) after having only killed a few deer. When he started making money on his rifles, he went on an African safari that supposedly would demonstrate hydrostatic shock on many animals. It didn't, and you can read all about it in the biography of Weatherby written by Grits and Tom Gresham, which contains a bunch of Weatherby's African journal. In fact ultra-high velocity with cup-and-core bullets was a dismal failure, especially on larger animals, and in his journal Roy keeps backpedaling by modifying his theory.

From my reading on bullet tissue-damage, cavitation can be a major factor in creating a larger wound channel, but it still isn't enough to short-circuit a deer's brain with a hit in the butt. What any of this has to do with tanks is a mystery.

Angus,

Your physics is pretty bad.

Yes but if we apply the same principles to humans and more specifically some campfire members (judging from some of the responses here), short-circuiting the brain from a hit in the butt becomes not only more likely but virtually assured.

I think this post is a good illustration 😀

Thank you, I work hard to fill my posts with useful information. Its nice to have some acknowledgement.

JB, I knew you knew that, and that you were just being a lot nicer about hitting the BS button than I am capable of being. I didn't know ol' Roy Weatherby was the guilty party for the propagation of that term. Interesting bit of trivia, that!

And I think your reading of temporary cavitation is pretty much correct, btw.





Thanks for the laugh, amigo.

As far as I can tell through reading old magazines and various books, several people got on the hydrostatic shock bandwagon. But Roy Weatherby spread it more than anybody else. He was a great salesman!

No worries mate. MD lobbed that one right down the middle.

"The Controversy Has Ended...."

Damn! Just when I sit back down with a fresh bowl of popcorn!


Ed

P O Ackley did his part to popularize the myth of hydrostatic shock when writing of .17 caliber rifles. "Hydrodynamic Shock" would have been a better term, but wouldn't change the physics that don't exist.

You did it now, Doc, hating on the Holy Grail, that "AI" dude....

I am glad you all debunked the high velocity small bullet theory. Thank you.

When I can I prefer a 45/70.

I am an e
Elmer Keith fan, hell I live near Salmon.

I remember the Tank Comanders roll their eyes about the fin stabilized sabot rounds.

It was an impressive visual when a fin stabilized sabot did its job on a turret though.

I never was in combat, so maybe some one wants to share.