"Gunshot Wounds" In

Shotgun shells loaded with rubber or plastic pellets Gunshot Wounds are designed for self-defense or for police riot-control purposes [1]. The cylindrical barrel may be slightly tapered toward the muzzle end (choke bore) in order Introduction to keep the discharged shot in a tighter spread over a longer distance. Firearm injuries are regarded as a special form of blunt trauma. The damage to the organism is caused by the impact of a single projectile (or a multitude Caliber of pellets) propelled from a barrel by high-pressure On the one hand, the term caliber represents the combustion gases and striking the body at a high diameter of the bore, and, on the other hand, the velocity. Gunshot wounds, in a broader sense, are bullet diameter. For metric calibers, the caliber spec- also lesions caused by blank-cartridge weapons as ifications are nominal values usually based on the well as injuries due to livestock stunners, stud guns diameter of the lands (maximum diametrical distance used in the construction industry, and similar devices. between the lands in the barrel). Most projectiles have a somewhat larger diameter. Example: The caliber Weapons and Ammunition 7.65 mm Browning has a land diameter of 7.63 mm, whereas the bullet diameter is 7.85 mm. The Anglo- Weapon Types American caliber specifications (in inches with 1 in. corresponding to 25.4 mm) are based rather on the Firearms enable the user to hit a target from a distance. Depending on the weapon type (see Firearms: bullet diameter. Overview), a distinction is made between handguns In pistols, the predominant calibers are 6.35 mm, (short-barreled firearms for use with one hand: pis- 7.65 mm, 9 mm, and .45 in, whereas in revolvers the tols, revolvers) and long arms (portable long-barreled main calibers are .32, .357, .38, and .44 in. firearms for use with both hands: rifles, submachine Cartridges for .22 caliber rimfire weapons can be guns, machine guns, and shotguns). fired not only from handguns but also from long Modern pistols carry a magazine in the handle; rifles (LRs). after firing a cartridge, its case is ejected as the bolt In cartridges designed for hunting rifles, it is usual is sliding back. Revolvers have a rotating cylinder to indicate not only the caliber but also the length of × × holding the cartridges; after firing the shot, the case the case in millimeters (e.g., 7 64 mm, 8 57 mm). remains in the chamber. The same applies to the cartridges of military rifles × × Weapons intended to be fired from the shoulder (e.g., 5.56 45 mm, 7.62 51 mm). have either a rifled barrel (see below), e.g., hunting The caliber of shotgun barrels is not identical with rifles (firing single projectiles) and military assault its internal diameter. It indicates the number of spher- rifles, or they have a smooth barrel such as shotguns ical lead balls collectively making up one English = (firing lead pellets, shotgun slugs, or rubber/plastic pound (1 lb 453.6 g) in weight; the diameter of pellets). these lead balls corresponds to the internal diameter of the barrel (e.g., 18.2 mm for shot caliber 12 and 16.8 mm for shot caliber 16). An exception to Rifled and Smooth Barrels this rule is the .410 shotgun, which is named after The inside surface of a rifled barrel has a spiral the barrel diameter in inches. pattern of elevations (lands) and grooves in between. As the bullet passes through the barrel, the lands cut Cartridges into the cylindrical part of the projectile, thus causing it to rotate around its longitudinal axis (“twist”). This The cartridges of handguns and rifles consist of a case gyroscopic spin stabilizes the bullet on its trajectory with a primer in its base, the propellant (gunpowder) and improves the accuracy of the shot. above, and a bullet (projectile). Shotguns have smooth-bore barrels without The case is usually made of brass. Cartridges for grooves and lands. They are designed for firing autoloading pistols have a groove just above the base shells containing mostly lead pellets or shotgun slugs. so that the fired case can be extracted and ejected by 2 Gunshot Wounds the recoiling slide. Revolver cartridges have a base 400 ms−1, whereas in hunting and military rifles it is plate that is wider than the cartridge case. considerably higher (approximately 700–1000 ms−1). The explosive compound is located in the base Generally, ammunition designed for autoloading of the cartridge case. When the trigger is pulled, the pistols and military rifles has full-jacketed bullets firing pin strikes the base of the case, causing the with a lead core and a jacket made of steel or a primer compound to detonate and initiate the burn of copper alloy covering the front and lateral parts of the gunpowder. the projectile but not its base. The primer consists of an explosive compound For hunting, most cartridges are equipped with a sensitive to percussion. Initially, the primer was semijacketed bullet. As the jacket is open at the tip, made of mercury fulminate, which was later replaced the projectile with its soft-point or hollow-point lead by a combination of chemical compounds typically core deforms more readily, thus transferring more containing the elements lead, barium, and antimony. energy to the animal body. Therefore, these elements play an important role in Standard .22 caliber rimfire ammunition usually the detection of gunshot residues (GSR). On the other has unjacketed lead bullets. Revolvers mostly fire hand, nowadays, lead-free primers are also available lead bullets, but also semijacketed projectiles. (e.g., “Sintox” with the main elements zinc and According to the bullet’s head configuration, there titanium). are different shape categories: round nosed, flat Above the primer, the case is filled with gunpow- nosed, pointed, cylindrical, and truncated cone. der (propellant), which does not detonate, but burns Apart from the shape and the design of the pro- rapidly. “Black powder”, which has been known for jectile, its mass and velocity are also of importance centuries and is a mixture of 75% potassium nitrate, for its potential effect. From the mass (m) and the 15% charcoal, and 10% sulfur, is rarely used as a pro- velocity (v), the kinetic energy Ek can be calculated (E = 1/2mv2); it is indicated in Joule (J). As exam- pellant nowadays (for historical or reproduced muzzle k ples, we may mention the mass of a .22 LR projectile loaders or some blank-cartridge weapons). Because of (2.55 g) and a 9 mm Parabellum projectile (8.0 g); in the high amount of solid combustion residues, a lot the first instance (.22 LR), the bullet energy is about of dense smoke is produced [2, 3]. 140 J, and, in the second instance (9 mm Para), about Currently, mostly smokeless powder is used as 430 J. The bullet energy of military and hunting car- propellant because of its higher efficiency of com- tridges is many times higher. Note that the energy bustion compared to that of black powder. It either increases exponentially with the velocity of the pro- consists of nitrocellulose (NC) alone (“single-base jectile. powder”) or of NC dissolved in nitroglycerine (“double-base powder”). The powder grains are of pale green color or have a shiny silver-black appear- Shotgun Ammunition ance (if coated with graphite). The powder particles Conventional shotgun shells are fired from smooth- resemble thin platelets (flake or disk powder), small bore shotgun barrels. Instead of a single projectile, spheres (ball powder), cylinders, or short tubes (tubu- they mostly contain numerous spherical pellets made lar powder). The individual powder particles have a from hard lead. The pellet diameter of birdshot varies diameter ranging from several tenths of a millimeter between 2 and 4.5 mm, and the pellet velocity on up to more than 1 mm. In Flobert cartridges (caliber leaving the barrel is about 300 ms−1. The larger the 6 or 9 mm), the primer also serves as propellant. pellet, the greater is its range, given the same velocity. The deflagration of the propellant produces an In addition to birdshot, cartridges with especially ample amount of gases (CO2,CO,H2,N2, nitrous large pellets (“buckshot”) are also available, with gases, water vapor), which are under high pressure single shotgun slugs (e.g., Brenneke type, Foster, and accelerate the projectile on its way through the Smith & Wesson sabot) and with rubber/plastic barrel. The processes inside the weapon itself are pellets. called interior ballistics (see Firearm Examination: The cartridge cases are made of cardboard or Ballistics). plastic and the floor (mostly consisting of brass) In handguns and .22 caliber rimfire rifles, the contains the primer. The space above it is filled with muzzle velocity typically ranges from 250 to a (smokeless) nitro powder, which is separated from Gunshot Wounds 3 the lead shot by intermediate layers (felt or plastic By firing test shots at “simulants” such as gelatin wad). Nowadays, the cardboard and felt wads have or glycerin soap, the transfer of kinetic energy in been largely replaced by plastic wads in connection biological soft tissue can be visualized, as the density with shot cups for the pellets. of these materials is similar to that of muscle. In contrast to elastic gelatin, soap shows an almost Wound Ballistics plastic deformation. The bullet path and the volume of the cavitation remaining after firing the shot is Exterior ballistics deals with the behavior of the pro- proportionate to the energy transferred [4]. jectile after leaving the barrel (trajectory, velocity A stable bullet with a low deformation potential etc.), whereas terminal ballistics covers the inter- (full-jacketed projectile, as used in military ammu- action between the projectile and the target (see nition) produces a “narrow channel” in the simulant Firearm Examination: Ballistics).

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