MikeG is correct, Easy. And here's the little bit of extra stuff that you forgot to quote in its entirety:
https://oa.doria.fi/bitstream/handle...pdf?sequence=1
Quote:
During penetration the bullet may lose its stability and start tumbling. It may also deform or be designed to expand controllably. Peters developed a mathematical model [Peters 1990] to predict the tumbling of a non-deforming bullet. A deforming bullet, however, will change its form and thus its centre of gravity during penetration making the model non-applicable as such. The forces acting upon the bullet may also tear it apart into fragments of various sizes.
The penetration behaviour depends on the bullet’s construction and on the retardation force it encounters. All these events make the bullet to present an increased cross-sectional area towards the penetration axis and thus transfer more of its kinetic energy into the tissue. Theb portion of the total kinetic energy that is transferred into tissue depends not on impact velocity or mass of the bullet per se, but on how the bullet behaves during penetration, whether it tumbles, deforms or fragments and what the tissue induced retardation force is. These phenomena make the bullet present a larger cross-sectional area in the direction of penetration thus increasing the drag and dissipation of kinetic energy [Sellier and Kneubuehl 1994, Tikka 1996].
The theory of Martel [Kneubuehl 1999] says
[6 ] Ed = Cv*V
, where Cv is a constant depending on the properties of the target material and V the volume of the ensuing hole. Therefore the size of the inflicted area is directly proportional to the dissipated energy Ed. Based on an analysis of a number of experiments with live pigs a significant correlation between the amount of devitalised tissue and dissipated kinetic energy(Ed) has been proved [Berlin et al. 1976 and 1979, Janzon and Seeman 1985, Janzon 1988, Tikka 1989, Janzon 2004]. Ed has also been called “down-track” energy [Coupland 2000].
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Most people are more concerned with what happens upon
impact.