Academic journal article Forensic Science Communications

Wounding Power of .315/8Mm Bullets Fired through Glass Windowpanes

Academic journal article Forensic Science Communications

Wounding Power of .315/8Mm Bullets Fired through Glass Windowpanes

Article excerpt

Abstract

In India, a .315 caliber sporting rifle is a very common licensed weapon. It, in conjunction with the soft-nose bullet, is often the weapon of crime in the northeastern region of India. Glass windowpanes are a common intermediate target for bullets or pellets and may become a secondary missile. Frequently, the glass serves as a clue in a criminal shooting investigation. This paper addresses the wounding potential and power of a soft-nose bullet at the striking velocity and the remaining velocity when fired through glass of various thicknesses.

Background

The physical characteristics of glass, such as its refractive index and density, are well known. Also well known is the behavior of a glass windowpane fracture under the stress of a bullet impact. Frequently, it is crucial to know the wounding capability of a bullet after it has perforated glass. In forensic ballistics, there is interest in investigating the relationship among the extreme ranges of various firearms and their wounding capability.

In the investigation of a crime when a person is alleged to have been shot through a glass door or window, it could be necessary to determine if the injuries were caused by the bullet that was fired through the glass. Since velocity is an important factor in the wounding power of a bullet, an answer could be found if the remaining velocity of the components of the soft-nose bullet, like the lead core or the jacket fragments after perforating the glass, is known. An investigation of forensic ballistics literature reveals that there is a lack of data on the velocity and wounding capacity of bullets that have perforated a glass window or door. Data about variables commonly encountered in shooting incidents should be collected, processed, and analyzed to provide accurate information about what occurred at the crime scene.

Sellier and Kneubuehl (1994) and Oven-Smith (1981) studied wounding power by experimenting with cloth, wood, and cadavers and comparing their findings with experiences on the battlefield. Many countries used full-lead round-nose bullets weighing between 20g and 25g with initial velocities of approximately 425m/sec. They concluded that in cases of physical injuries and skull wounds, the hydraulic pressure caused by the projectile is important and that some of the lead from the projectile might melt on impact with the bone but not during penetration into soft tissue.

Sellier and Kneubuehl (1994) experimented with the properties of small-arms projectiles. They also studied the effectiveness of jacketed, nonjacketed, and semijacketed bullets that were propelled from the rifle into the human body.

McLaughlin and Beardsley (1956) experimented with what takes place when a bullet passes through a glass intermediary target. They studied the distribution of gunpowder residue on the glass and on cloth targets after test firings. They found that the glass was intact except for the hole caused by the bullet. Although it has been discussed, there is a paucity of information in forensic science literature concerning the effect of intermediate targets on bullets.

Fackler (1994) studied energy expenditure and suggested that much of the energy is dissipated as heat during the creation of the hole. Some of the heat could be from chemical energy, often transformed directly into heat. Some of the heat could be a final product of the expenditure of kinetic energy. In short, the heat resulting from the projectile's mechanical disruption of matter (e.g., air, flesh, or a glass target) gives further injury to the human body.

Depending on its shape, a moving object loses velocity, thus energy, because of air drag. The efficiency of the shape depends upon the flow of air across the object; efficient shapes disturb the airflow very little, whereas inefficient shapes disturb the airflow more (Harrison 1971). A high-speed projectile fired from a great distance may cause an irregular wound entrance as it enters the skin over a bony surface (Hather 1987). …

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