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December 9, 1988

Wound Ballistics

Author Affiliations

Parkway Medical Center State College, Pa

Parkway Medical Center State College, Pa

JAMA. 1988;260(22):3277. doi:10.1001/jama.1988.03410220061022

To the Editor.—  The article entitled "Wound Ballistics" by Dr Fackler1 spends a paragraph "proving" that a spherical shot causes a cavity 11 to 12.5 times larger than the shot itself and thereby "disproving" "the common misconception" of a 30-fold difference claimed by Amato et al.2 This article's conclusion is based on diameters, or more accurately heights, of the spheres and the temporary cavities. However, cavities have width as well as height and depth: a temporary cavity is a function of the depth of penetration and the cross-sectional area measured at right angles to the line of penetration. The cross-sectional area is, in turn, not a function of the diameter of the cavity but the square of its radius.To use the data of Amato et al, the radius of a 6.4-mm steel sphere is 3.2 mm; the cross-sectional area of the permanent cavity then becomes equal to