hydrostatic shock or not?

[George]

The subject of hydrostatic shock came up in another thread. Most people apparently believe ML guns don’t create it, but I disagree with that. I put together what are for me clues supporting my conclusion, collected over several years.

Just from curiosity, in 2014 I had a session of shooting gallon milk jugs filled absolutely with water, using my 20 gauge smoothie, range 50 yards, .600” PRB, MV 1475 fps, velocity at striking 1075 fps. All jugs were exploded into shreds, water showered my Jeep which was standing 15 feet away.



As a control I shot the same load from 7 yards, velocity on striking about 1400 fps, at an empty gallon jug, top screwed tightly on. No exploding, just a clean entry and exit hole.

Entry:


Exit:


A little while after that I shot a half-gallon milk jug filled with water with my .30 caliber rifle from 15 yards, MV 2120 fps. The entire top half of the jug was shredded, the top 2”, including the cap, disappeared.

All my ML deer have been shot with either .54 or .62 caliber, except one. In 2012 I killed a fat buck with my .40 caliber rifle, range 50 yards, 92 grain PRB, MV 2100. In cleaning I noticed something I had never seen in any of my ML deer shot with larger balls. There was a definite streak of chewed up meat along the track of the ball.

Proof positive for me was a doe I killed in 2005. I shot her directly between the eyes at 30 yards with my 20 gauge smoothie, .600” PRB, MV 1475 fps, velocity on striking about 1200 fps. I couldn’t believe the result. The doe’s head looked as though the top had been sawed cleanly off. Everything from her eyes up was gone, only the two depressions of the brain pan remained. Every bit of brain, tissue, muscle, tendon, fascia, bone and hair had been completely removed. I found a palm-size piece of her skull lying by a tree 12 feet behind her, and every scrap of tissue was gone from it, only pink bone remained, The tree and nearby brush were sprayed with blood, brain and tissue, so finely divided that I didn’t notice it until I was cleaning up my mess after hanging and butchering the doe.

Notice the strange depression in front of her ears. There should be head there.



Nothing except a wave of pressure generated by the passage of the ball could have caused all these results. It’s called hydrostatic shock. I think it happens, alright, but just not to the degree with faster smokeless rounds. I think it causes damage along the track of the ball, in some cases, depending on where in the deer it strikes, stretching the tissues to the point of rupturing blood vessels and contributing to the deer going down.

Spence

 

[Black Hand]

Water is minimally compressible. The impact force of the projectile must be/is transferred to the water, which propagates the force outward causing the jug to explode.

 

[azmntman]

I agree Spence. Your experimenting is good proof. However I make my comments based on my experience shooting deer with CF and ML rifles. I dont lose much meat AT ALL with a ML but even a rib cage shot deer using a hi power CF means gross jelly like stuff :barf: Anyone try a 25lb block of ice? I have not but sure remember the hunter safety course range day when the instructor hit it with a 30-06!

I would sure like to have seen that doe skull! A buddy borrowed my .54 and hit a buck between the eyes at like 90 yds +/- so I will have to ask him about the destructiveness. IRCC he said not so much but a MUCH smaller PRB and a lot further off than your doe.

 

[rodwha]

Hmmm... I looked up the wiki on hydrostatic shock. It seems I misunderstood this to some degree, but I also see, according to it that it doesn’t quite fit this either.
https://en.m.wikipedia.org/wiki/Hydrostatic_shock_(firearms)

I had always figured it was the hyper velocity that created the huge permanent cavity. We certainly see bullets will create a large temporary cavity that shrinks down once things settle down, which is what seems happened to the deer’s skull. Being bone it certainly didn’t allow any give and so gave. We see the evidence of such in the military testing.

Crazy how that doe’s top was elsewhere! I wouldn’t have expected that.

 

[rodwha]

Forgot to mention the jug test...

I’m completely at a loss for why the faster projectile made a clean hole whereas after it slowed down considerably it blew the top off.

 

[tenngun]

Well I won’t venture anything on the math, just say that in ballistic jel it sure looks like hydraulic shock. With or with out it turns deer French.

 

[Elnathan]

Spence,

I believe that what you are seeing is hydraulic shock, not hydrostatic shock. Hydrostatic shock is when the shockwaves from the bullet travel through the flesh and blood vessels and screw with the neurological system - i.e, a bullet through the chest causes the brain to shut down. What you are describing is a temporary wound channel that exceeds the capacity of the surrounding material (bone, plastic) to move in the necessary time.

I have to admit that I, too, had the two slightly confused when I wrote my initial comment, and since I had been told that extensive testing had recently demonstrated that lower velocity rounds did not cause hydrostatic shock, I took that as my starting point and worked from there.

Turns, out, BTW, that it isn't that simple - while 2600fps is generally the minimum cutoff for hydrostatic shock, the minimum velocity needed declines somewhat when bullet diameter increases, so it is possible that a very fast-moving roundball (1800fps or above) may induce it.

Source: https://www.ballisticstudies.com/Knowledgebase/Effective+Game+Killing.html

Another article from the same source that might be of interest is one on flat-nosed bullets: https://www.ballisticstudies.com/K...the+meplat+on+terminal+ballistics+-+full.html

Both are primarily concerned with modern guns, but since there doesn't seem to be much written about roundball terminal ballistics we have to take what we can get, I think. I wouldn't be surprised to learn that a round ball or traditional conical has a lot in common with flat-nosed modern bullets.

 

[Vaino]

Hydrostatic shock is a controversial theory and not proven one way or another. Gunshot wounds in humans were analyzed by pro and con doctors and scientists and nothing was proven.

The proponents of hydrostatic shock believe it's actually a hydraulic force in soft tissue and has nothing to do w/ bone.

The jugs {blue} you show first look different than the one that's got the single hole......having been in plastics for many yrs, some plastic is more brittle than others.

Let's just say that projectiles hitting animals do kill them......asking why gets into many fields of study and outside of blood loss, destroying a vital organ or hitting the brain and forward portions of the spinal cord, nothing has been proven asre "hydrostatic shock"......Fred

 

[Skychief]

To all, Spence's photo of the jug with a clean hole through two of its sides was filled with air in lieu of water, if I read correctly. It was shot as a control.

 

[George]

I’m completely at a loss for why the faster projectile made a clean hole whereas after it slowed down considerably it blew the top off.

There was no water in that jug with the clean hole. It served as a baseline or control. Can't have hydrostatic anything without the hydro. :grin:

Spence

 

[George]

Hydrostatic shock is when the shockwaves from the bullet travel through the flesh and blood vessels and screw with the neurological system - i.e, a bullet through the chest causes the brain to shut down.

The science of hydrostatics has to do with fluids which aren't moving. It isn't always related to hunting.

Spence

 

[coloradoclyde]

As a bullet passes through tissue at high velocity (or a water jug), A powerful vacuum is created behind the bullet....Air rushes in behind it to equalize the pressure and everything expands. This causes the jug to explode and/or a large wound cavity to be created.

Also, the "hydrostatic" element refers to a fluid not a liquid. Water is a liquid but air is a fluid. The Hydrostatic element is air, not water.

 

[rodwha]

No hydro without water for certain! Reading comprehension is a golden thing to have!

 

[hawkeye2]

"A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure."

Fluid: a substance (as a liquid or gas) tending to flow or conform to the outline of its container; specifically : one in the body of an animal or plant

fluid: A state of matter, such as liquid or gas, in which the component particles (generally molecules) can move past one another. Fluids flow easily and conform to the shape of their containers.

Note that a fluid in the form of a gas is compressible, as a liquid it is not. There really isn't much difference between the two but it would make for a lively discussion around the campfire. As an aside when I worked in a lab for a jet engine manufacturer I had to test many finely divided solids for particle size distribution and I observed some that approximated the flow characteristics of a fluid.

"Hydraulic shock is the civil engineers term also known as water hammer but in terminal ballistics context refers to the pressure of accelerated fluid particles that create the temporary wound channel.

Hydrostatic shock transfer refers to the effect when shock waves travel through flesh to distant nerve centers, disrupting their ability to emit electrical impulses.

Be very much aware that the terms hydraulic and hydrostatic shock are quite often misused by both hunters and professionals - including ballisticians working for bullet making companies."*

*Terminal Ballistics Research
https://www.ballisticstudies.com/Knowledgebase/Effective+Game+Killing.html

 

[coloradoclyde]

Imagine if you will;
Air (a compressible fluid) rushing into a void in water (an incompressible liquid) at supersonic speed.

Imagine the results.

 

[hawkeye2]

The shock wave of it's passage, not unlike a sonic boom, will displace a volume of water creating a cavity that'll collapse as fine bubbles. The displaced water creates an area of increased pressure which transfers energy from the area close to the bullet's path to the surrounding area that could cause a lot of damage, think a depth charge near a submarine. Depending on how fast the cavity collapses I wonder if that could also cause damage to the surrounding tissues. I wonder if there might be cavitaiton, like the collapsing bubbles that eat up a boat's propeller. It's also very possible that I'm thinking too hard as it's way past my bed time. :grin:

 

[Black Hand]

Note that a fluid in the form of a gas is compressible, as a liquid it is not. There really isn't much difference between the two but it would make for a lively discussion around the campfire.

Perhaps in chemical composition - Yes (think of liquid water compared to steam).

However, their physical characteristics are different - Liquid water occupies far more of the "space" in a given volume than steam (more molecules of water per a given volume than molecules of water as steam per a given volume).

 

[BrownBear]

I dunno where to draw the line between yes and no. I've followed the wound channel on virtually every large animal I've dressed over the last 60 years. It's pretty evident with modern ammo out to some long range, but then the signs in flesh go away as distance increases.

That's significant because those long range shots without signs of shock pretty much resemble what I see with muzzleloaders. The exception is with muzzleloaders at really close range. I'd have to draw the line for the calibers and animals I've shot at about 20 yards. Inside that, yeah. Beyond that, I'm not good enough to spot it.

So based on a whole lot of animals and guns, I'd have to say hydrostatic shock from muzzleloaders is mostly a no, with a little bit of yes thrown in up close.

 

[George]

As a bullet passes through tissue at high velocity (or a water jug), A powerful vacuum is created behind the bullet....Air rushes in behind it to equalize the pressure and everything expands.

You need to think about what happens to create that "powerful vacuum". A pressure wave created by the ball striking incompressible fluid knocks the fluid/tissue aside, leaving an empty spot, THEN the air rushes in. The vacuum is the result of the pressure wave, not the cause of it. I think that if any tissue damage occurs, it's from that same pressure wave.

Spence

 

[Loyalist Dave]

Actually the current theory is that HS is linked to the cycle of the cardiovascular system, and where that cycle is at the impact of the projectile. The lower velocities of black powder projectiles then not having nearly enough ability to cause an overpressure, thus it's much less likely that a patched round ball will cause HS. Other variables, however do apply.

LD