Stopping Power by Caliber Part 2

[JASmith]

...What is your opinion on hydrostatic shock as a means of inflicting a wound?...

Gene,

I had believed that hydrostatic shock was very important from the late '50s when I read the reports of how devastating the .17 caliber rifles were on feral burros in the Southwest. Comments like "the blood coming out as a single organ" during the skinning and butchering were rather convincing.

After reading Fackler's and others' reports, I have come to realize that hydrostatic shock was not the source of the injuries. The massive internal bleeding was most likely caused by massive fragmentation of the small projectile probably coupled with secondary fragments from bone impact.

Consider a broadhead hunting arrow -- game seems to go down as quickly when properly hit just the same as with hunting bullets. How much hydrostatic shock does the arrow produce?

...a major role with supersonic rifle ammunition but very little role with subsonic pistol ammunition...

I made the earlier comment about breaking kidney stone using sonic pulses because they are described as being significantly more intense than the shock waves generated by bullets.

One of my favorite pastimes is busting water-filled containers (don't get a lot of hunting opportunities these days). I've noticed that 6 oz through 1 gallon containers show nice violent disruptions when hit by .308/30-06/7.62X54R rounds - the 5.56 is a little less vigorous on the 1 gallon containers but do well on 2-quart items. Five gallon and larger containers just seem to grunt when hit by the 30-caliber bullets even though the bullets cut multiple holes in the container allowing the water to drain. These observations combined with discussions here and reading of critiques of high-speed film "documentation" hyping the dynamic cavity and hydrostatic shock leads me to some conclusions about the dynamic cavity.

1. These critiques suggest that the dynamic cavity is not particularly important for hits on the torso. (Hits on extremities are a different matter, I think.)
   
2. The critical literature doesn't go far enough to explain what's happening (e. g. why do prairie dogs and other small animals seem to explode when hit by high velocity rounds?
   
3. The size of the fluid-filled object matters. Whenever the dynamic cavity is large enough to cause the container to split, it comes apart nicely. The smaller containers show more spectacular results.
   
4. The squirrel and prairie dog have volumes under about 2-quarts while the targets in our discussion are more like 10 gallons when one subtracts the volume of extremities from the 15-20 gallon volume of a 150 lb individual, so we can readily visualize the analogy.
   
5. The relevant damage to living targets with 5-gallon and larger is almost all a result of cutting and tearing by the bullet, fragments, or secondary bone fragments.
   

So, the conclusion appears to be that the supersonic (in air only) rifle bullet brings more mass to the problem and enough energy to cause lots of primary and secondary fragments. The cutting and tearing caused by these is what does the damage...

Cheers!
Joe