TYPES OF FIREARMS
Very generally, irearms can be divided into two types: handguns and shoulder irearms. Handguns include revolvers and pistols, while shoulder irearms are more diverse, encompassing riles, shotguns, machine guns, and submachine guns. A broad knowledge and familiarity with the various types, makes, models, and styles of firearms is crucial to being a successful forensic irearms scientist. This knowledge and familiarity should cover not only new products as they emerge on the market, but also older models and the history of manufacturers and their products. Each year, at the Shooting, Hunting and Outdoor Trade Show and Conference (SHOT Show), hundreds of exhibitors, many of them firearms related, display their new products and give out product information; in 2002, thousands of people attend the show. The SHOT Show is an excellent source of information about irearms and related products Handguns are irearms designed to beired with one hand. They appear in two major types: revolvers and (semi)automatic pistols (see Figure 1(a) and (b)). A revolver is a handgun that feeds ammunition into the firing chamber by means of a revolving cylinder. The cylinder can swing out to the side or be hinged to the frame and released by a latch or a pin for loading and unloading. A single-action revolver requires that the hammer be cocked each time it is fired; a double-action revolver can be cocked by hand or by the pulling of the trigger, which also rotates the cylinder. A (semi)automatic pistol, on the other hand, feeds ammunition by means of a spring-loaded vertical magazine. Although the term “automatic” is often applied to pistols fed by magazines, they are not truly automatic in theiriring. An automatic firearm is one that continues to fire ammunition while the trigger is pressed; a semiautomatic firearm fires one bullet for each pull of the trigger. When fired, semiautomatic pistols use the energy of the recoil and the sliding of the breech block (slide) or the recoil of the cartridge to expel the empty cartridge from the firearm and load a live round into the firing chamber. Springs are used to store the energy and expend it. Shoulder arms consist of riles, automatic friles, machine guns, and shotguns. Riles are designed to be fired from the shoulder with two hands (see Figure 2(a) and (b)). Riles may be single-shot, repeating, semiautomatic, or automatic. A single-shot rile must be loaded, fired, the cartridge extracted, and then reloaded; this type of rile was common as a young boy’s irst firearm just after the turn of the century but is almost nonexistent now. Repeating riles ire one bullet with each pull of the trigger, but the expended cartridge must be expelled, the firing mechanism cocked, and a live round reloaded from a magazine manually. Repeating riles may be bolt-action (like the M1 from war movies or many hunting riles) or lever-action (made popular by cowboy movies). Semiautomatic rifles use the energy of the fired ammunition to expel the empty cartridge, cock the firing mechanism, and reload a live round; thus, one pull of the trigger fires one round, and this may be done sequentially until the magazine is empty. Assault friles, like the AK-47 or M-16, can beired either like semiautomatic friles or in automatic mode: Pull the trigger, and the firearm will ire ammunition continuously until all the ammunition is gone. A machine gun is a fully automatic ire arm and therefore is fed ammunition from a high-capacity belt or box. Because of their size and the strength of the recoil, machine guns are meant to be fired from a tripod or other mounted/fixed position. A submachine gun is a machine gun meant to be fired while held in the hands.
FIGURE 1 (a) A revolver is a handgun that feeds ammunition via a revolver cylinder (hence the name), while (b) a pistol feeds ammunition through a spring-loaded magazine.
FIGURE 2 Rifles are firearms designed to be fired with two hands, one to pull the trigger, the other to stabilize the barrel for aiming. Rifles can be single-shot, repeating, or assault rifles (a, b).
