A firearm is a type of machine that utilizes a barrel and a mechanism to convert the potential energy of gunpowder into the kinetic energy of a projectile. It is fundamentally composed of a receiver, a barrel, and a stock.
Core Structural Components
- Receiver: Considered the basic unit of a firearm, it houses the firing and breech mechanisms and is the point where the barrel and stock are assembled.
- Barrel: The metal tube through which a projectile or shot charge is fired.
- Muzzle: The end of the barrel from which the bullet exits.
- Breech: The opposite end of the barrel, which is attached to the action.
- Stock: A frame made of wood, metal, or plastic that holds the barrel and action, allowing the shooter to hold the weapon firmly.
- Butt or Butt-stock: The specific portion of the gun that is held against the shoulder or grasped.
- Grip: The handle of a handgun or the portion of the stock behind the trigger on a long gun.
Internal Barrel Characteristics (The Bore)
The bore refers to the inside of the barrel, which can be smooth (as in shotguns) or contain rifling.
- Rifling (Lands and Grooves): Spiral grooves cut into the barrel to impart a spinning motion to the bullet. Lands are the raised portions between these grooves.
- Caliber: The diameter of the bore in a rifled firearm, usually measured from land to land and expressed in hundredths of an inch or millimeters.
- Gauge: The diameter of a smoothbore shotgun barrel, historically determined by the number of lead balls of that diameter required to weigh one pound.
The Firing Mechanism and Action
The action is the part of the firearm that loads, fires, and ejects a cartridge.
- Chamber: The portion of the action that holds the cartridge in position, ready for firing.
- Breech Face: The area surrounding the firing pin that sits against the head of the cartridge during the firing process.
- Firing Pin (Striker): The part of the mechanism that strikes the primer of a cartridge to initiate ignition.
- Trigger: The part moved manually by the finger to discharge the firearm.
- Hammer: A device that strikes the firing pin or cartridge primer to detonate the powder.
- Sear: A part of the firing mechanism that holds the hammer in place until the trigger is pressed.
- Bolt: A mechanism that supports the cartridge head and often contains the firing pin, extractor, and ejector.
Ammunition Handling and Safety
- Magazine: A container that holds ammunition before it is loaded into the chamber.
- Cylinder: Found in revolvers, this part holds multiple cartridges in individual chambers that rotate into the firing position.
- Extractor and Ejector: The extractor withdraws the cartridge from the chamber, while the ejector expels it from the firearm.
- Safety: A manual or automatic mechanism designed to prevent the accidental firing of the gun.
- Sights: Devices located on top of the barrel used for aiming.
- Silencer: A device fitted over the muzzle to muffle the sound of the gunshot by baffling the escape of gases.
Refrence :
- Sharma, B.R.; “Firearms in Criminal Investigation & Trials”, Universal Law Publishing Co Pvt Ltd, New Delhi, 4th Edition, 2011.
- Heard, B.J; “Handbook of Firearms and Ballistics”, John Wiley, England, 1997.