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From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Newsgroups: rec.guns
Subject: Re: The Speed of Sound
Message-ID: <35682@mimsy.umd.edu>
Date: 15 Jun 91 02:56:19 GMT
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#In article <35658@mimsy.umd.edu> ke4zv!gary@gatech.edu (Gary Coffman) writes:

##In article <35545@mimsy.umd.edu> bercov@bevsun.bev.lbl.gov 
##(John Bercovitz) writes:

##Another thought mentioned in this group at times is that a supersonic
##bullet causes shock waves when it enters a semi-liquid medium.  It's
##certainly true that anything traveling faster than the speed of sound
##in a medium has shock waves coming off of it.  But the speed of sound 
##in water is around 5000 fps.   A critter with a projectile traversing
##his carcass is going to experience traumatic shock but not shock waves.
##Perhaps that's the source of the confusion 'mongst the gun rag writers.
##Nitpicking: It is possible to get some very small local shock waves
##at the front of a flat-nosed bullet if it is only slightly subsonic
##in the traversed medium.

#I believe you, but I've seen high speed shadowgraphs of bullets that
#had what definitely looked like shock waves trailing from the nose.

Those bullets were supersonic because they were traveling through air
which, of course, has a lower speed of sound.

#I've also seen boats moving considerably slower than 5000 fps with
#the same sort of "bow wake" as the bullet had. 

That's a different phenomenon but there's some amazing similitude there,
huh?  There's a reason for that.  Maybe someone can tell us what it is.

#I've dressed enough game to know that *something* damages a
#conical section of meat surrounding the wound channel.
#So if this isn't a sonic boom style shock wave, what is it?

I see a bullet traversing the euphemism as primarily a momentum transfer
problem.  This is because the forces involved in the momentum transfer
are much higher than the forces involved in destroying the structural
integrity of the euphemism.  So I would say the wound channel is the
result of all the little dMs (that's dee masses) becoming sub-miniature 
secondary projectiles.  But I'm just guessing.  However, the drag function
of a bullet in ballistic gelatin tends to agree with this analysis.  
Perhaps Peter Kasler could enlighten us?

     JHBercovitz@lbl.gov    (John Bercovitz)