This study of the penetrating power of modern police ammunition when it hits various types of exterior house walls is intended to help police agencies assess the risk of a stray police bullet injuring an innocent individual inside a residence, as well as to provide information on the capabilities of various ammunition that is intentionally fired at an armed person behind an exterior wall.
The specific purpose of the study was to determine the perforation potential and exit velocity (if perforation is achieved) of various calibers and bullet types of modern police ammunition when fired in police issue handguns. The testing required the construction of wall units with siding types that consisted of stucco, vinyl siding, and cedar siding. A wood frame was constructed of 2" x 4" lumber to hold both a wall unit and the two chronograph screens. The shots were fired at the wall units at a distance of 10 feet from the outer wall unit surface. Five firearm types were used to fire various bullets in the following categories: .40 Smith and Wesson, 9 mm Para., and .38 Special. Four shots were fired with each ammunition type through the stucco and vinyl wall units, and five shots were fired through the cedar siding units with each ammunition type. All bullets in all tests were slowed by the walls as they were perforated by the bullets. The walls with the stucco surface slowed the bullets the most. In most cases, the cedar siding walls slowed the bullets more than the vinyl siding. On visual observation and comparison of the exit holes in the gypsum wallboard compared with the entrance holes in the siding, there did not appear to be much expansion of the jacketed bullets (hollow points). A comparison of the exit velocities of the bullets in this experiment with the results of a bullet speed/tissue penetration study done by DiMaio et al. in 1982 gives an indication of the danger that a person behind such exterior walls would face. The DiMaio study shows that a .38 caliber bullet traveling as slow as 191 feet per second will perforate skin and penetrate tissue up to 40 mm (approximately 1 1/2 inch). All of the firearm/ammunition combinations fired through all wall types in this study, with one exception, exceeded this bullet speed. Tables and 4 references