Types of Firearm Weapons

A general knowledge of firearms and ammunition is required to determine the extent of damage caused by gunshot wounds. The five categories of small arms are handguns, rifles, shotguns, submachine guns, and machine guns (DiMaio, 1999; Merck, 2013). Projectile wounds encountered in veterinary medicine are most commonly caused by handguns, rifles, shotguns, and air guns (Bradley-Siemens & Brower, 2016; Bradley-Siemens et al., 2018). Low-velocity weapons can include handguns and air-powered guns with a projectile velocity around 1000 feet/second. High-velocity weapons can include handguns and rifles with a projectile velocity of 2500 feet/second or higher (Merck, 2013).

The caliber of a weapon is based on the diameter of the bore of the gun measured from land to land. It is the diameter of a barrel before the rifling is created. Caliber designations are given in inches or as metric units. An example of the former using inches includes the 0.38 Special, 0.45 ACP, or a 0.357 Magnum, and the latter metric units include 9x18 mm Makarov or 5.56 x 45 mm (Bradley-Siemens & Brower, 2016; Bradley-Siemens et al., 2018). An example of both the American system in inches and metric system used in Europe is the famous James Bond gun, the Walther PPK, referred to as a 0.32 ACP or 7.65 mm.

Handguns

The most common types of handguns in the United States are revolvers and auto-loading pistols (semi-automatics and rarely automatics) (DiMaio, 1999; Bradley-Siemens & Brower, 2016; Bradley-Siemens et al., 2018). Handguns have rifled barrels. A revolver has a revolving cylinder with multiple chambers, and each chamber will contain an individual cartridge. The cylinder rotates mechanically to line up each chamber with the firing pin and the barrel. A pistol has a magazine holding multiple cartridges. The magazine is usually seated in the hand grip of the pistol. Handguns may be considered high- or low-velocity weapons depending on caliber and load (DiMaio, 1999; Merck, 2013; Bradley-Siemens & Brower, 2016; Bradley-Siemens et al., 2018).

Air, Gas, or Spring Guns

Air-, gas-, or spring-powered weapons range from toys to highly powerful pistols and rifles. Air rifles use the expanding force of compressed air or gas to propel a projectile down a rifled barrel. An air gun is differentiated from and air rifle by its smooth-bored (non-rifled) barrel. In a spring-powered gun, a cocking action is used to put a firing pin under spring pressure which strikes the projectile upon pulling the trigger. The same type of projectiles can be used in these types of weapons (Bradley-Siemens & Brower, 2016; Bradley-Siemens et al., 2018). Air, gas, or spring guns, like handguns, are usually considered low-velocity weapons (DiMaio, 1999).

Rifles

A rifle is a weapon designed to be fired from the shoulder. Rifles are used for greater distances and have more precision and accuracy than handguns. In the United States rifles have a minimum legal barrel length of 16 inches. There are multiple types of rifles including hinged or single shot, lever action, bolt action, pump action, and auto loading (DiMaio, 1999; Bradley-Siemens & Brower, 2016; Bradley-Siemens et al., 2018). An auto-loading rifle can either be semi-automatic or automatic. In a semi-automatic rifle, the weapon fires one round each time the trigger is depressed. In an automatic, the weapon will continue to fire rounds as long as the trigger is depressed or until the weapon runs out of ammunition (DiMaio, 1999; Bradley-Siemens & Brower, 2016; Bradley-Siemens et al., 2018). Rifles have rifled barrels and are generally considered high-velocity weapons (DiMaio, 1999; Bradley-Siemens & Brower, 2016).

Shotguns

A shotgun is fired from the shoulder. The barrel of a shotgun is generally smooth bored; no rifling is present. Rifled barrels are available for use with slugs. A shotgun barrel diameter is called a gauge, most commonly either 10, 12, 16, 20, or 28 gauge, although other sizes do exist. Gauge more appropriately refers to the weight of a solid metal sphere that fits into the barrel of a gun, and this weight is determined as a fraction of a pound. An example is a one-twelfth pound ball fits a 12-gauge bore. Shotguns are used for dispersal of shots on a moving target at short distances. A shotgun can fire multiple types of ammunition (shells), including pellets, buckshot, and slugs. In the United States, federal law mandates a barrel length of no less than 18 inches for shotguns. Shotgun barrels are available in several choke sizes: cylinder bore (no choke), improved cylinder choke, modified choke, and full choke, that influence the dispersal pattern of shotgun pellets. A shotgun may also have a device known as a variable or adjustable choke or interchangeable choke tubes attached to the barrel that can switch between different chokes without switching barrels. This may affect the interpretation of the range of discharge in a shotgun wound (DiMaio, 1999; Merck, 2013; Bradley-Siemens & Brower, 2016; Bradley-Siemens et al., 2018).