page_title: Gun barrel
section_title: Muzzle
hierarchical_section_title: Gun barrel / Components / Muzzle
context_page_description: A gun barrel is a crucial part of gun-type ranged weapons such as small firearms, artillery pieces and air guns. It is the straight shooting tube, usually made of rigid high-strength metal, through which a contained rapid expansion of high-pressure gas is ifsfe w propel it out of the front end at a high velocity. The hollow interior of the barrel is called the bore, and the diameter of the bore is called its caliber, usually measured in inches or millimetres.
  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 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.
context_section_description: The muzzle is the front end of barrel from which the projectile will exit.  Precise machining of the muzzle is crucial to accuracy, because it is the last point of contact between the barrel and the projectile. If inconsistent gaps exist between the muzzle and the projectile, escaping propellant gases may spread unevenly and deflect the projectile from its intended path (see transitional ballistics).  The muzzle can also be threaded on the outside to allow the attachment of different accessory devices.
  In rifled barrels, the contour of a muzzle is designed to keep the rifling safe from damage by intruding foreign objects, so the front ends of the rifling grooves are commonly protected behind a recessed crown, which also serves to modulate the even expansion of the propellant gases.  The crown itself is often recessed from the outside rim of the muzzle to avoid accidental damage from collision with the surrounding environment.
  In smooth bore barrels firing multiple sub-projectiles (such as shotgun shot), the bore at the muzzle end might have a tapered constriction called choke to shape the scatter pattern for better range and accuracy.  Chokes are implemented as either interchangeable screw-in chokes for particular applications, or as fixed permanent chokes integral to the barrel.
  During firing, a bright flash of light known as a muzzle flash is often seen at the muzzle.  This flash is produced by both superheated propellant gases radiating energy during expansion (primary flash), and the incompletely combusted propellant residues reacting vigorously with the fresh supply of ambient air upon escaping the barrel (secondary flash).  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.  Flash suppressors or muzzle shrouds can be attached to the muzzle of the weapon to either diminish or conceal the flash.
  The rapid expansion of propellant gases at the muzzle during firing also produce a powerful shockwave known as a muzzle blast.  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.  Accessory devices such as muzzle brakes and muzzle boosters can be use to redirect muzzle blast in order to counter the recoil-induced muzzle rise or to assist the gas operation of the gun, and suppressors (and even muzzle shrouds) can be used to reduce the blast noise intensity felt by nearby personnel.
caption: Muzzle of a SIG 550 rifle, equipped with a birdcage-type flash suppressor
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