Flash hider

A flash suppressor, also known as a flash guard, flash eliminator, flash hider, or flash cone, is a device attached to the muzzle of a rifle that reduces its visible signature while firing by cooling or dispersing the burning gases that exit the muzzle, a phenomenon typical of carbine-length weapons. Its primary intent is to reduce the chances that the shooter will be blinded in low-light shooting conditions. Contrary to popular belief, it is only a minor secondary benefit if a flash suppressor reduces the intensity of the flash visible to the enemy.

A flash suppressor is different from a muzzle brake, although they are typically mounted in the same position and sometimes confused with each other. While the former is intended to reduce visible flash, a muzzle brake is designed to reduce recoil inherent to large cartridges and typically does not reduce visible flash.

Pre-20th century rifle designs tended to have longer barrels than modern rifles. A beneficial side effect of the long barrel is that the propellant is completely burned before the bullet leaves the barrel, usually resulting only in a puff of smoke from the muzzle. However, if the same weapon's barrel is "cut down" (shortened), as is common in cavalry and jungle-combat adapted versions, the bullet would often leave the barrel before the powder was completely consumed, resulting in a bright flash from the muzzle.

When barrel lengths were dramatically decreased with the introduction of various shorter-barreled rifles and carbines, the flash became a serious problem during night-time combat, as the flash would imperil the shooter's night vision and would also make the shooter's position more apparent. Originally limited to "special purpose" roles, it was now expected that all infantry weapons with shorter barrels would experience this problem, and thereby be of limited use in low-light situations. Flash suppressors became common on late-World War II and later assault rifle designs, and are almost universal on these weapons today. Some designs such as those found on the AKS-74U serve a dual-role as a gas expansion chamber helping the shortened weapon's gas system function properly.

Military flash suppressors are designed to reduce the muzzle flash from the weapon to preserve the shooter's night vision, usually by diverting the incandescent gases to the sides, away from the line of sight of the shooter, and to secondarily reduce the flash visible to the enemy. Military forces engaging in night combat are still visible when firing, especially with night vision gear, and must move quickly after firing to avoid receiving return fire.

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