Gun barrel
It is the straight shooting tube, usually made of rigid high-strength metal, through which a contained rapid expansion of high-pressure gas(es) is used to propel a projectile out of the front end (muzzle) at a high velocity.
The first firearms were made at a time when metallurgy was not advanced enough to cast tubes capable of withstanding the explosive forces of early cannons, so the pipe (often built from staves of metal) needed to be braced periodically along its length for structural reinforcement, producing an appearance somewhat reminiscent of storage barrels being stacked together, hence the English name.
[3] Bronze and brass were favoured by gunsmiths, largely because of their ease of casting and their resistance to the corrosive effects of the combustion of gunpowder or salt water when used on naval vessels.
The later-invented breech-loading designs provided a higher rate of fire, but early breechloaders lacked an effective way of sealing the escaping gases that leaked from the back end (breech) of the barrel, reducing the available muzzle velocity.
[7] A gun barrel must be able to hold in the expanding gas produced by the propellants to ensure that optimum muzzle velocity is attained by the projectile as it is being pushed out.
[8][9] Fluting is the removal of material from a cylindrical surface, usually creating rounded grooves, for the purpose of reducing weight.
Most common form of composite barrel are those with carbon fiber sleeves, but there are proprietary examples such as the Teludyne Tech Straitjacket.
Structurally, the chamber consists of the body, shoulder and neck, the contour of which closely correspond to the casing shape of the cartridge it is designed to hold.
The rear opening of the chamber is the breech of the whole barrel, which is sealed tight from behind by the bolt, making the front direction the path of least resistance during firing.
The crown itself is often recessed from the outside rim of the muzzle to avoid accidental damage from collision with the surrounding environment.
The size of the flash depends on factors such as barrel length (shorter barrels have less time for complete combustion, hence more unburnt powder), the type (fast- vs. slow-burning) and amount of propellant (higher total amount means likely more unburnt residues) loaded in the cartridge.
The audible component of this blast, also known as a muzzle report, is the loud "bang" sound of gunfire that can easily exceed 140 decibels and cause permanent hearing loss to the shooter and bystanders.
The non-audible component of the blast is an infrasonic overpressure wave that can cause damage to nearby fragile objects.
