Effects of Range, Caliber, Barrel Length, and Rifling on Pellet Patterns Produced by Shotshell Ammunition

Abstract The effects of range, caliber, barrel length, and rifling on the scatter of shotshell ammunition were investigated. A series of shots was fired from three .22-caliber weapons and two .38-caliber weapons at six ranges varying from 0.3 to 6.1 m (1 to 20 ft). The spread of each shot-shell pattern was measured by taking the square root of the area of the smallest rectangle that would just enclose the pellet pattern. Regression analysis was applied to the variation of pattern spread as a function of range. A linear relationship was found to represent adequately the variation of pattern spread with range. Of the handguns tested, the weapons with the shorter barrel lengths produced the larger pellet patterns, and when the barrel lengths were similar, the larger caliber handguns produced the larger pellet patterns. The competing effects of barrel length and muzzle velocity are also discussed.