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From: bercov@bevb.bev.lbl.gov (John Bercovitz)
Newsgroups: sci.military
Subject: Re: Using the rifle suited to the previous war?
Message-ID: <1991Jan19.040344.4228@cbnews.att.com>
Date: 19 Jan 91 04:03:44 GMT
References: <1991Jan5.021828.27885@cbnews.att.com> <1991Jan17.054422.29971@cbnews.att.com>
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From: bercov@bevb.bev.lbl.gov (John Bercovitz)
In article <1991Jan17.054422.29971@cbnews.att.com> !simnet@ssc-vax (Mark R Poulson) writes:
>
>There are two important areas to consider ballistically. First, wounds are
>usually much more severe when the bullet strikes its target with a velocity
>greater than 2100 f/s (the speed of sound in water/flesh). Secondly, bullets
>drop with range. Both of these points are better with high muzzle velocities
>and high sectional densities (i.e bullets that are heavy in relation to their
>caliber).
>

On the 2100 fps: I don't think so.  The speed of sound in a liquid, according
to my old Sears & Zemansky physics book is SQRT(B/rho) where B is the bulk
modulus which is the inverse of the ISENTROPIC compressibility, in this case,
and rho is the density of the liquid, all at the appropriate temperatures.
I don't have too much data on water at 37C, but I have some for 20C, which
should be close enough.  Roughly, salt water has a density of 64 lbm/ft^3 and
you can convert this to rho by remembering to divide by gravity in the English
system ('cept the English disowned it so it must be Mare-kin) getting
9.59^-5 lbf-sec^2/in^4.  Then you get the isentropic compressibility of sea-
water out of your CRC or some such place and invert it and convert it remem-
bering there are 6895 N/m^2 to a lbf/in^2, you get 344,000 psi.  Then the
speed of sound in saltwater at 68F must be:
SQRT(344,000 psi/9.59^-5 lbf-sec^2/in^4) = 59900 in/sec = 4990 fps.   '-)
             Q.E.D.
  JHBercovitz@lbl.gov