<P> 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 convex 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 . </P> <P> In smoothbore barrels firing multiple sub-projectiles (such as shotgun shots), 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 . </P> <P> 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 propellent 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 . </P> <P> 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 exceeds 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 personnels . </P>

Where is the muzzle located on this firearm