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Old October 6, 2012, 12:47 PM   #5
481
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Join Date: April 18, 2011
Posts: 469
Quote:
Originally Posted by webleymkv:
Dr. Roberts' work, along with others like Duncan MacPhearson, Shawn Dodson, and the FBI, is based heavily upon that of Dr. Martin Fackler. Unfortunately, many if not most of the "experts" whose opinions are based on the work of Dr. Fackler take his conclusions to logical extremes and fail to explain, or perhaps even understand, how and why Dr. Fackler came to those conclusions to begin with.

For example, many want to discount temporary cavitation, and by extension kinetic energy transfer, all together because Dr. Fackler said that it was an unreliable wounding mechanism at handgun velocities. What seems to be lost, however, is that just because something is unreliable that does not mean that it is non-existant.
I never got that impression from reading some of their works.

In fact, MacPherson states on pages 7 and 8 of "Bullet Penetration"-

Quote:
"Any attempt to derive the effect of bullet impact in tissue using energy relationships is ill advised and wrong because the problem cannot be analyzed that way and only someone without the requisite technical background would try. Many individuals who have not had technical training have nonetheless heard of Newton’s laws of motion, but most of them aren’t really familiar with these laws and would be surprised to learn Newton’s laws describe forces and momentum transfer, not energy relationships. The dynamic variable that is conserved in collisions is momentum; kinetic energy is not only not conserved in real collisions, but is transferred into thermal energy in a way that usually cannot be practically modeled. The energy in collisions can be traced, but usually only by solving the dynamics by other means and then determining the energy flow.

Understanding energy and how it relates to bullet terminal ballistics is useful even though energy is not a useful parameter in most small arms ballistics work
.”
And Schwartz states on page 7 of "Quantitative Ammunition Selection"-

Quote:
"While a projectile in motion possesses both momentum and kinetic energy, the penetration of a transient projectile through a homogenous fluid or hydrocolloidal medium constitutes an inelastic collision mandating that it be treated as a momentum transaction. Therefore, a momentum-based analysis of projectile motion is the most equitable approach in constructing a terminal ballistic performance model.

Although it may be possible to devise a mathematical model based upon the expenditure of a projectile’s kinetic energy as it traverses a medium, there is nothing to be gained from the pursuit of such an unnecessarily complex approach
."
From what I can tell, it appears that neither is saying that KE transfer doesn't count, but rather that KE transfer is just not a very feasible/efficient way to analyze the problem.

Does that make sense the way I said it?
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