Firearms

A firearm is a weapon of attack or defense that expels a projectile via the action of the force exerted by the gases resulting from the rapid combustion of an explosive mixture. A firearm is often associated with the commission of a violent crime and is commonly found at crime scenes or on suspects. Also, many people who commit suicide use a firearm. An interest in firearms in forensic sciences is therefore, paramount. In criminalistics , the study of firearms consists first in the knowledge and identification of firearms and their ammunition, second in the internal, external, and terminal ballistics , and finally in the analysis of powders, primers, and their residues.

The birth and evolution of firearms is directly linked to the discovery of black powder. It is believed that the discovery of black powder dates from 1242, when the French monk Roger Bacon (1214–1294) wrote a letter describing the recipe for black powder. At that time, it was composed of about 40% saltpeter (potassium nitrate), 30% charcoal, and 30% sulfur. The first barrels, ancestors of the modern firearms, were developed at the beginning of the fourteenth century. At that time, the barrel was loaded from its end (muzzle), first with powder, and then with the projectile. The powder was ignited with a match, which was connected to the powder through the base of the barrel. Around 1800, mercury fulminate started to be used and the first primers were developed. In 1835, French arms manufacturer Casimir Lefaucheux (1802–1852) invented the first metallic cartridge. One year later, in 1836, American arms manufacturer Samuel Colt (1814–1862) invented the revolver. The pistol was invented prior to that time, however, it was loaded by the end of the barrel. The modern semi-automatic pistol (using a magazine) was invented after the revolver in 1893.

A firearm expels a projectile at high velocity. The projectile is part of the cartridge. The cartridge consists of a shell holding the primer at one end and the projectile on the other with powder in the middle. The cartridge is inserted either manually or automatically in the barrel of the firearm. The trigger of the firearm is then pulled, which arms the hammer. At some point, the hammer is released and hits the firing pin, which hits the primer. The shock to the primer starts its combustion, which, in turns, ignites the powder in the cartridge. The powder combusts very rapidly and produces gases, which increase the pressure inside the cartridge (and therefore the barrel) tremendously. This pressure is in the order of 2,000–4,000 atmospheres. This pressure is exerted on the base of the projectile, which is pushed into the barrel. The projectile then exits the barrel at high velocity, usually ranging from 250–1,000 meters per second (273–1094 yards per second).

Firearms are classified in two main categories: light and heavy firearms. Light firearms include handguns and shoulder guns. Handguns are then further classified into revolvers, pistols (semi-automatic, automatic, and machine), and Derringers (single-shot and double-barreled pistols). Shoulder weapons are divided into two subcategories: weapons with a rifled barrel, such as rifles and carbines, and weapons with a smoothbore barrel, such as shotguns. It is important to understand that some shoulder weapons may have more than one barrel. They can have two or more one-over-the-other barrels or side-by-side barrels. There are some shoulder weapons that have a combination of rifled and non-rifled barrels. Among the rifled shoulder weapons are the semi-automatic and automatic assault rifles and machine guns. Usually, heavy weaponry includes weapons that shoot calibers above 12.7 millimeter and are found on vehicles or armored tanks. These are specialized, usually military, weapons and are not encountered in the daily routine of a crime scene unit. Finally, there is the category of improvised or homemade weapons, which includes an enormous variety of different weapons of all calibers and functions.

Firearms are characterized by many variables, such as brand, model, size, length of barrel, shape, color, and functionality. Some of the most important variables of the firearm are the general rifling characteristics (when dealing with a rifled barrel), which include the caliber , the direction and degree of twist, and the number and width of grooves and lands. The caliber is correlated to the barrel's diameter and the power of the cartridges for which the firearm is designed. With few exceptions, a firearm is designed to use one given caliber. Upon shooting a projectile, the firearm leaves impressions on the projectile and the cartridge's casing. The observation of these impressions allows the forensic scientist to establish a link between the firearm and the elements of ammunition.

When dealing with a firearm found at a crime scene or on a suspect, the first security measure is to consider it as loaded and ready to shoot. Security with firearms is paramount and must be prioritized over everything else. If the firearm has just been found at a crime scene, it is possible to sketch, photograph, and take notes about it before touching it. Then, it is either placed in a container specifically designed to transport firearms and resist accidental discharges, or it needs to be secured. The firearm is then transported to the forensic laboratory where the firearms and toolmarks examiner can examine it.

see also Ballistics; Crime scene reconstruction; Drugfire; Integrated Ballistics Identification System (IBIS); Microscope, comparison; Trajectory.

firearm Term used usually to describe a small arm – a weapon carried and fired by one person or a small group of people. Firearms were used in Europe in the 14th century. They were, however, ineffective in close combat until c.1425, when a primitive trigger to bring a lighted match into contact with the gunpowder charge was invented. Such firearms, called matchlocks, were heavy and cumbersome, and needed a constantly lit match. The lighter flintlock (which used the spark produced by flint striking steel to ignite the powder) superseded the matchlock in the mid-17th century. During the 19th century there were great changes. In 1805, the explosive properties of mercury fulminate were discovered and, together with the percussion cap invented in 1815, it provided a surer, more efficient means of detonation. It permitted the development by 1865 of both the centre-fire cartridge (which has been the basic type of ammunition used in firearms ever since) and breech loading, not previously practicable. Another major 19th-century advance was rifling – the cutting of spiral grooves along the inside of a barrel in order to make the bullet spin in flight. During the 1830s, Samuel Colt perfected the revolver, a pistol which could fire several shots without the need to reload. By the 1880s, magazine rifles were also in use, and became more effective with the introduction of a bolt action after 1889. Development of a weapon that could fire a continuous stream of bullets began with the manually operated Gatling gun, but the first modern machine gun was the Maxim gun, invented in the 1880s, which used the recoil energy of the fired bullet to push the next round into the breech and recock the weapon. Guns of this type dominated the trench warfare of World War I. By World War II, more portable automatic weapons, such as the Bren gun and sub-machine gun, were in use. Newer developments include gas-operated rifles, firearms with several rotating barrels and extremely high rates of fire, and small firearms that use explosive bullets.

firearm device consisting essentially of a straight tube to propel shot, shell, or bullets by the explosion of gunpowder . Although the Chinese discovered gunpowder as early as the 9th cent., they did not develop firearms until the mid-14th cent. By that time, firearms, particularly in the form of heavy cannon, were in general use in Europe and Asia Minor. With such firearms, the Ottoman Turks captured Constantinople. From the 15th cent., when the matchlock appeared, to the end of the U.S. Civil War, firearms became increasingly important in battle, and military tactics had to adapt constantly to successive improvements in their design. The early matchlocks, which depended on a lit match for firing the gunpowder, were supplanted first by flintlocks (perfected at the turn of the 17th cent.) that used a striking flint for firing, and then by various breach-loading firearms (perfected in the middle of the 19th cent.), which used bullets fitted with shells full of gunpowder that was ignited by the impact of a firing pin. In the 15th cent. firearms also came into use in hunting . Firearms were spread throughout the world during the period of European expansion. In some areas they were rapidly integrated into the existing culture and economy. Firearms are generally classified either as large firearms, i.e., artillery , or as small arms .

firearms were first imported into Ireland late in the 15th century, just as their efficiency improved. Artillery (siege and field guns), belonging mostly to the state, was introduced by Gerald FitzGerald ( Gearóid Mór), 8th earl of Kildare. He battered down fortresses, beginning at Balrath Castle in Westmeath in 1488, on annual journeys across the country. Towns bought guns for defence: in 1495 Waterford sank one of Perkin Warbeck's ships in an exchange of fire. Artillery coming into Gaelic hands was used mainly against local rivals.

Despite a 1494 statute restricting possession of artillery and firearms to the lord deputy and his licensees, it was impossible to stop proliferation. The first recorded use of a handgun was in 1487 when Godfrey O'Donnell killed an O'Rourke. Garret Mór himself died from a gunshot wound gained in battle with the O'Mores. Firearms—handguns, then arquebuses, calivers, and muskets—redressed the state monopoly in artillery by aiding traditional Irish guerrilla tactics. They assisted successful ambushes of Sussex at Kiltubber, Co. Galway, in 1558 and near Armagh in 1563. By the Nine Years War ‘shot’ composed a third of the opposing forces; by the Confederate War two‐thirds of the combatants had guns.

Hiram Morgan

fire·arm / ˈfī(ə)rˌärm/ • n. a rifle, pistol, or other portable gun.

firearm n. a rifle, pistol, or other portable gun.

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