What is hydrostatic shock?

Not technically a shock wave. That is when something, a bullet say, travels through a medium faster than the speed of sound in that medium. The medium can't get out of the way fast enough, so gets compressed, if it is compressible, forming a Mach cone trailing behind. Possibly the opposite of a temporary wound channel. Not going to happen at any credible rifle velocity.

Hence the crack from supersonic rifle bullets, that's not possible to moderate, only the shock and pressure waves at the muzzle.

A giveaway on the battlefield, or urban areas with a gun problem. Modern kit can identify the shooter's position rather precisely, hence interest in subsonic stuff for special forces.


I don't know the speed of sound in flesh, guessing that it's at least 4000 fps, since it's mostly water, salty at that, hence I doubt that a true shock wave has anything to do with this.

In air, the speed is roughly 1125 fps. Water 4858 fps. Salty water even faster. Slightly depending on temperature.

Back in the day military researchers used to experiment on live pigs. Nowadays they also have lots of data from the effects on humans, gathered from recent conflicts. That would be interesting if ever made publicly available.

I think there is a confusion between "shock" as in "it died of shock", wound channels, bullet performance, and how they impact the anatomy whilst occurring. Calling any of this "shock waves" is incorrect IMO, that's something quite different, and I don't think happens, except during the secondary ballistics phase, through the air. What actually happens at the terminal phase (well named) is still rather a mystery I think, for us, and largely luck-of-the-draw, notwithstanding best efforts with bullet, calibre and placement decisions. Gelatin blocks aren't the same as real animals.

Being hit by any bullet, air rifle or even shotgun pellet would of course be "shocking". Game birds seem to tumble over readily enough with just a few bits of shot at energies below what we are told is suitable for rabbits with airguns. Headshoot rabbits and watch them jump around all over the place, they are dead, in the brain, but the other bits of nervous system haven't stopped working. Just as deer should be treated carefully, even if headshot, don't immediately start grallocking, move the hind legs and you might get a kick in the face from the "reflexes" left working, or so I've been warned.

Target shooting is much easier to understand and try to analyse to multiple significant digits IMO with all the gadgets and software available. Punching a hole in paper, banging a gong, knocking down a pop-up, doesn't require any thought about the terminal phase, nor consideration of exactly where to place the shot. Trying to combine the two with one rifle and load, well I'd suggest bullet choice is everything.

Same as shooting in the field is completely different from at the range. Different techniques.

I do hypothesise that disrupting activity in critical nerve plexuses is very relevant, however it happens. It doesn't take much energy, as you will know if you've ever been "winded" by e.g. a punch to the solar plexus, learned boxing or just scrapping. Add a big hole from an expanding bullet through something major, not just a thump from a padded boxing glove, or a bare fist, and it would very soon be over, rather than just incapacitation for five minutes or so.
 
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Not technically a shock wave. That is when something, a bullet say, travels through a medium faster than the speed of sound in that medium. The medium can't get out of the way fast enough, so gets compressed, if it is compressible, forming a Mach cone trailing behind. Possibly the opposite of a temporary wound channel. Not going to happen at any credible rifle velocity.
Snip...

I don't know the speed of sound in flesh, guessing that it's at least 4000 fps, since it's mostly water, salty at that, hence I doubt that a true shock wave has anything to do with this.

In air, the speed is roughly 1125 fps. Water 4858 fps. Salty water even faster. Slightly depending on temperature.

snip...

Prompted by your post I looked at the (same?) Wikipedia article to confirm, and came to a slightly different conclusion than you.


The bullet may not be travelling fast enough to generate a "shock wave" travelling through flesh. However the shock wave accompanying it prior to strike, providing the bullet was still travelling supersonically, will still be hitting the target...no? I presume the pressure differential of the Mach cone is what we see apparently rippling out from the strike point in those slo-mo films.

It is the same conical shock wave that is sensed by the Steinert Chronograph...


True the pressure wave that the bullet creates within the flesh whether Hydrostatic or Hydraulic may well not technically be a "shock wave" just a wave that shocks the animals system.

Alan
 
There's a lot of energy dissipated in the shock wave / Mach cone. Concorde, and fighter planes can do great damage when they go supersonic in the wrong places, not just broken windows but livestock aborting etc. Still compensation being paid out for that in training areas when the pilots get a bit gung-ho and over-do it.

Our newer VLD/ELD bullets are designed around this, the "drag" isn't so much simple aerodynamics as you might think, it's mostly due to energy dissipation creating the shock wave. Clever shaping of the bullet can reduce this very significantly. It started with putting boat-tails on, but has got much more scientific nowadays.

Conversely purpose-designed subsonic stuff can be very slippery, it just keeps trundling along slowly, albeit dropping under gravity at the same rate as anything else, just over a longer time hence further. Really clever stuff can make the transition from super to sub sonic without too much upset, but most can't.

You can make your bullets out of lead (least expensive), gilding metal, copper, titanium, aluminium, bronze, depleted uranium, bismuth, even platinum (according to Hillaire Belloc). Everything has been tried. All have different characteristics and applications.

I think that the supersonic shock wave might be "hitting the target" as well, at least that portion that doesn't fly past it, having already expanded at the Mach angle. Quite how much energy there is left in that portion I wouldn't like to speculate. Enough to stun a Wallaby ?

Study manufacturers' data on retained energy at a distance for their ammo, then assume that the "drag" is basically the energy lost creating the shock wave, compared with at the muzzle. Mach angle increases as the velocity drops, until it becomes 180 degrees inclusive at the super-sub transonic region. Like I said, you can actually see this happening through a spotting 'scope, on the range, when the humidity is high and the sun is in the right direction. It looks like a faint doughnut following the bullet, and can show roughly where the shots have gone, before the target markers have done their job.

Shooting tracer is great fun, where permitted, and can demonstrate a few things about how bullets actually fly through the air, what the wind does to them, or what happens when they bounce off hard things like shingle. Perhaps we need some ELD hunting bullets with tracer, a market opportunity ? Pre-cooked meat, or forest fires also resulting.
 
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Modern kit can identify the shooter's position rather precisely, hence interest in subsonic stuff for special forces.

It's always been pretty much thus so. Mortar locating systems (by radar plotting) such as Cymbeline and Green Archer which it was at that time replacing were "old hat" back in the day when I was in my youth plus a (acoustic) rifle shot locating device that I can't recall the name of.
 
In essence it is the trauma caused by small capillaries bursting and so leading to hemorrhage and death. The pressure which is induced in the CNS and circulatory system by the bullet strike and transfer of some of this energy which is transmitted through the fluids. In case of lung capillaries they may be only one or two cells thick so are easily ruptured. If you think that the surface are of a lung is almost that of a tennis court then huge fluid loss reults hence speedy death.

D
 
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