Generally, a Firearm is a device so designed that may propel a projectile with abundant force. The required ‘force’ is generally produced by the creation and expansion of gases produced by the burning of powder charges i.e., Propellants present inside the cartridge.
So far, Air Guns such as Rifles or Pistols are concerned, the said necessary force is provided either by Compressed Air or gases like Carbon Dioxide or Nitrogen.
A firearm is called as the firearm because it’s flame that is responsible for the burning of propellant to create sufficient gas to drive the projectile.
It is a device by which a projectile or projectile can be hurled with great force. This general definition includes not only familiar hand weapons including the revolver, the pistol, the rifle, and the shotgun but also the machine gun and an extensive variety of military artillery. The latter class of weapons is the concern of ordinance experts. Moreover, the crimes committed with these weapons are not very common. The only important types of firearms encountered in the criminal investigation will be the subject matter of the discussion that will follow.
Modern firearms are classified based on several characteristics. The classifications are neither comprehensive nor quite systematic. The following characteristics form the basis for their classification.
• Handling characteristics: Handguns, shoulder arms.
• Bore characteristics: Smooth bore and rifled bore firearms.
• Loading characteristics: Muzzle loading, breech-loading, or magazine loading firearms.
• Action characteristics: Lever action, bolt action, self loaders, automatics.
• Firing characteristics: single shot, repeaters.
• Use: sporting firearms, service firearms.
It is an important firearm, which falls in the category of shoulder arms. All shotguns are smoothbore firearms. Smooth Bore Firearm is the one in which, the Bore, or inside of the barrel, is perfectly smooth from Breech end to the Muzzle end. For illustration, if the barrel of a shotgun is cut up cross-sectionally, it will be a perfect ring.
They are known as shotguns because they fire a single ball, slug, or a charge consisting of a considerable number of lead pellets. A shotgun may be single or double-barreled. The barrels may be joined side by side or they may be one over the other. The double-barreled guns are either hammer or hammerless types, the latter being the more modern type. In hammer guns, the hammers are cocked with the hand. In hammerless the hammer action is enclosed in the body of the gun and the hammers get cocked automatically when the breech is opened and closed.
The shotgun barrels have varied bore diameters and are designated by a number and gauge or bore. Thus, in a 12-bore shotgun, the internal diameter of the barrel is equal to the diameter of a spherical lead ball made of pure lead and twelve such lead balls, which correspond to the diameter of the barrel and together weigh a pound. A 12 bore shotgun will have 0.729 inches bore diameter. There are 10 gauges, 16 gauges, 20 gauges, and 28 gauges shotguns.
Shotgun barrels are often narrowed down to reduce the diameter of the barrel near the muzzle, to control the dispersal of the shot charge, and thus increase the effective range. This constriction is known as choke and varies from 1 to 0.25mm. There is a full choke, modified choke, improved cylinder, and true cylinder guns.
The two ends of the barrel of a shotgun are called the breech and the muzzle end. The breech end is also known as the chamber end. The breach end of the barrel has a special cavity to house a cartridge. The chamber end carries extraction and ejection mechanisms.
When the cartridge is loaded from the breech end it is known as a breech-loading firearm. All modern firearms, whether rifled or smooth bore is breech-loading weapons. Shotguns of muzzleloading type are also known. In this, the cartridge components are loose and inserted from the muzzle end. A ramrod attached to the gun is used to position various components.
The Breech-loading smoothbore firearms are in vogue at present and their good examples are:
A. SBBL – It is a Single Barrel Breech Loading shotgun that has a single barrel making it capable to house only one cartridge at a time to its chamber present at the Breech end.
B. DBBL – It is a Double Barrel Breech Loading shotgun that has two barrels and is capable to stock not more than two cartridges at a time.
Muzzle Loading Shotguns
The Muzzle loading shotguns are obsolete nowadays because of their primordial mechanism in which the Gun powder was rammed into the barrel through the muzzle end and then single ball ammo placed above the charge.
The escape of gases made the weapon dangerous and prone to accidents. Moreover, the range was not as much as expected and making their lethality less.
There are some drawbacks to shotguns;
• One of them is the loading capacity of a shotgun.
• Usually, the numbers of cartridges available in the gun are not more than the maximum number of the barrel.
• For repeated firing shotguns surely lack quality.
Muskets are evolved in the 16th century and were replaced by rifles in the 19th century. The earlier musket were matchlock weapons replaced by flintlock in the 17th century.
Early musket work is often handed by two-person and fired from a portable wrist. The weapon used by typically 5.5 feet long and weighed 20 pounds. The musket has long bore stalled and usually taken bayonet at the muzzle needed for firing spherical. There is no system of choke in the musket. The bore of the gun is 0.410 inches equal to 67 bores.
The muzzle velocity of a single ball is from 1600 to 1800ft/sec. Letters types were smaller and lighter and accurate to hit a human target at 800 yards. These had caliber ranging from 0.69 to more than 0.75 inches. It could fire six rounds in a minute using the prepared cartridge. Modern muskets are smooth bored weapons that are shoulder arms used by the army and police.
All rifled arms fire a single bullet. They have a much longer barrel and can fire high-powered ammunition. Rifles are characterized by their calibers. The caliber is the actual measure of the bore diameter of the barrel between two opposite lands. The caliber is measured in decimals.
The rifled barrels are grooved. The grooves are cut in the form of spirals from inside the bore. The raised parts between these are known as lands. The number of grooves in a rifle varies. The width of the grooves in the barrel is cut in various ways. The spiral groove is obtained by gradually and uniformly turning the cutter while cutting the groove. This turning is called the twist and the angle of the turning is called the pitch.
The rifling in the barrel gives gyratory motion to the projectile, which continues even in flight. The gyratory motion maintains the bulletin stable nose-end flight, which reduces the air resistance and enhances the degree of accuracy.
Rifles are of different actions. The most common are bolt action and semi-automatic action. In bolt action loading and unloading operations are carried out through a bolt with a knob. The firing pin assembly remains inside the bolt. The bolt head is fitted with an extractor, 0.303, 0.22 are examples of rifles.
Guns are operated by using a single hand. It has a short barrel therefore these have an effective range of a hundred meters.
Basically, they are of two types:
A revolver is a rifled handgun, which has a revolving cylinder having chambers for loading the cartridges. The number of chambers may vary from four to seven. On pressing the trigger the cylinder rotates thereby bringing one of the chambers in line with the barrel for firing. Revolvers of different calibers are available.
The revolvers have short barrels and, therefore, are effective only at short ranges. The barrel of a revolver, which has six lands and grooves and a left-hand rifling twist is known as Colt type and that which has five lands and grooves and a right-hand twist is known as Smith and Wesson type. The barrels of revolvers like rifles have four to seven grooves.
There is some space between the barrel and the revolving cylinder, which is responsible for the leakage of gases and powder residues, thereby reducing its effectiveness. The same powder sometimes gets deposited on the hand of the shooter.
Revolvers are both double action and single action. When the trigger of a double-action revolver is pressed, it rotates the cylinder containing the live cartridge and brings one of the chambers in line with the barrel, simultaneously, cocking the hammer and releasing it for firing.
In single-action revolvers, the hammer is cocked manually, which rotates the cylinder to bring one of the chambers in line with the barrel. The pressing of the trigger is utilized to release the hammer for firing.
All short-barreled rifled arms, which can be fired by one hand are known as pistols. The revolver also is a pistol. But because of a revolving cylinder, it is known as a pistol-revolver. Pistols have a magazine that is enclosed in its grip. These are available in all calibers from about 5 to 12mm.
Pistols are normally semi-automatic or self-loader type, in which with the pull of the trigger a cartridge is fired. The discharge is utilized for ejecting the fired cartridge case, reloading a fresh live round in the chamber, and cocking the action so that the weapon is automatically made ready to fire again on pulling the trigger a second time.
True automatic pistols are also known, in which with the pull of the trigger all the loaded cartridges in the magazine get fired one after the other and stop only when the trigger is released. 7.65mm, 9mm mouser pistols are examples of pistols.
Improvised firearms are also known as homemade firearms as they are manufactured by local blacksmiths or illegal manufacturers from easily available household materials. These materials may be iron pipes, car steering pipes, and hose pipes, etc. with crude tools for the firing mechanism. The caliber, shape, and size of the firearm depend upon the availability of the ammunition, barrel tube, and the skill of the blacksmith. There are large variations in the mechanism in the functioning of the firearms and it varies not only from the standards but also from one firearm to another.
These firearms are unique in themselves concerning mechanisms of firing and general makeup. The country-made firearm is generally short-barreled to facilitate concealment. They are usually smooth barreled and are chambered for a different types of cartridges.
Caliber is the diameter of a rifled firearm. It is usually expressed in hundredths of an inch or millimeter.
For example; 0.22 cal and 9mm.
Gauge is the diameter of a smooth barrel weapon. Originally the number of lead balls with the same diameter as the barrel that would make a pound.
For example; A 12 gauge shotgun would have a bore diameter of a lead ball 1/12 pound in weight the only exception is the 0.410 shotgun, in which the bore size is 0.41 inches.