A muzzle shroud, linear compensator, blast shield, forward blast diverter or concussion reduction device (CRD) is a sleeve (either circular or otherwise) that attaches to and extends beyond the muzzle of a

firearm A firearm is any type of gun designed to be readily carried and used by an individual. The term is legally defined further in different countries (see Legal definitions). The first firearms originated in 10th-century China, when bamboo tubes c ...

in order to redirect some of the

noise Noise is unwanted sound considered unpleasant, loud or disruptive to hearing. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference aris ...

and concussion, or

shock wave In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a med ...

, from the

muzzle blast A muzzle blast is an explosive shockwave created at the muzzle of a firearm during shooting. Before a projectile leaves the gun barrel, it obturates the bore and "plugs up" the pressurized gaseous products of the propellant combustion behind i ...

forward and away from the shooter, and other bystanders, behind and to the sides. A muzzle shroud is similar to a

barrel shroud A barrel shroud is an external covering that envelops (either partially or full-length) the barrel of a firearm, to prevent unwanted direct contact with the barrel (e.g. accidental collision with surrounding objects, or the user accidentally tou ...

with the difference being that it only surrounds the far end of the barrel ( muzzle). It can be a muzzle extension or muzzle device, and can also be considered a

flash suppressor A flash suppressor, also known as a flash guard, flash eliminator, flash hider, or flash cone, is a muzzle device attached to the muzzle of a rifle that reduces its visible signature while firing by cooling or dispersing the burning gases that ...

without circumferential openings. A muzzle shroud differs from a silencer (sound suppressor) in that its primary function is not to suppress the sound, but merely redirect it so to increase the comfort of the shooter, reducing the concussion to a comfortable level. Linear compensators are also a form of muzzle shrouds. While most muzzle brakes redirect the gases to the side and rearward, most linear compensators redirect the gases forward. Linear compensators and suppressors do not have the disadvantages of a redirected muzzle blast; they actually reduce the blast by venting high pressure gas forward at reduced velocity A muzzle shroud can be used in conjunction with other muzzle devices (such as a

muzzle brake A muzzle brake or recoil compensator is a device connected to, or a feature integral to the construction of, the muzzle or barrel of a firearm or cannon that is intended to redirect a portion of propellant gases to counter recoil and unwant ...

flash hider A flash suppressor, also known as a flash guard, flash eliminator, flash hider, or flash cone, is a muzzle device attached to the muzzle of a rifle that reduces its visible signature while firing by cooling or dispersing the burning gases that ...

or a brake/hider hybrid device). This way the user can still benefit from some of the recoil reduction of a muzzle brake, but with less of the noise and concussion normally associated with such a device. However, depending on the design, the CRD will usually increase the recoil to some degree compared to using a muzzle brake only.

Motivation

Even wearing double hearing protection (

earplug An earplug is a device that is inserted in the ear canal to protect the user's ears from loud noises, intrusion of water, foreign bodies, dust or excessive wind. Since they reduce the sound volume, earplugs are often used to help prevent hearin ...

s and muffs), some shooters have experienced hearing loss from high volume or long term shooting, probably due to the shockwaves from muzzle blasts propagating though the

sinuses Paranasal sinuses are a group of four paired air-filled spaces that surround the nasal cavity. The maxillary sinuses are located under the eyes; the frontal sinuses are above the eyes; the ethmoidal sinuses are between the eyes and the spheno ...

and facial bone structures. The noise levels experienced are often increased when firing indoor or in other confined spaces. Sound suppressors are increasingly commonly used by shooters to reduce the concussion and thereby prevent hearing loss, but are not always suitable for either legal or technical reasons. Suppressors can either be difficult or illegal to obtain in some jurisdictions, while a concussion reduction device is normally not classified as such. Concussion reduction devices also typically don't have the problem of introducing the extra amount of

mirage A mirage is a naturally-occurring optical phenomenon in which light rays bend via refraction to produce a displaced image of distant objects or the sky. The word comes to English via the French ''(se) mirer'', from the Latin ''mirari'', mean ...

as a suppressor does, since suppressors work by absorbing heat from the burnt gunpowder. The extra mirage can make accurate aiming difficult, especially on precision targets at long range. A muzzle shroud can also increase comfort compared to a muzzle brake while shooting

prone Prone position () is a body position in which the person lies flat with the chest down and the back up. In anatomical terms of location, the dorsal side is up, and the ventral side is down. The supine position is the 180° contrast. Etymolog ...

by preventing dust to kick up from the ground.6 of the Best Muzzle Blast Control Devices Available - Ballistic Magazine
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Amount of noise reduction

Sound waves In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the ...

are semi- directional. They consist of both Point- and Line-wave propagation. The

projectile A projectile is an object that is propelled by the application of an external force and then moves freely under the influence of gravity and air resistance. Although any objects in motion through space are projectiles, they are commonly found in ...

emanates mostly line-

propagation Propagation can refer to: *Chain propagation in a chemical reaction mechanism *Crack propagation, the growth of a crack during the fracture of materials *Propaganda, non-objective information used to further an agenda *Reproduction, and other forms ...

properties after leaving the barrel. At the moment that the projectile is exiting the

barrel A barrel or cask is a hollow cylindrical container with a bulging center, longer than it is wide. They are traditionally made of wooden staves and bound by wooden or metal hoops. The word vat is often used for large containers for liquids, ...

it produces a mainly point-biased wave generation. (This is largely due to the

shock waves In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a me ...

traveling forward along the interior of the barrel, thus preventing any backward travel from the projectile into the barrel.) Sound waves travel in an ever-expanding bubble emanating from the muzzle when the

propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the e ...

gases are traveling at

supersonic Supersonic speed is the speed of an object that exceeds the speed of sound (Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately . Speeds greater than five times ...

speeds. This is called the "muzzle blast." Except in extremely low

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and ...

loads, the exiting propellant gasses generate much higher sound pressure levels ( dBa) than any other aspect of the weapon firing. (e.g., hammer, sear, bolt, supersonic flight signature, etc.) The supersonic "ballistic crack" is typically 136-138 dB, whereas "muzzle blast" may reach 168 dB. By encircling the muzzle, the shroud funnels and focuses the sound waves along the projectile flight axis, away from the shooter. This alone can partially protect the shooter from 12 to 18 dB of blast returning to the shooter's ears.

Legality

United States

In the United States, the

ATF The Bureau of Alcohol, Tobacco, Firearms and Explosives (BATFE), commonly referred to as the ATF, is a domestic law enforcement agency within the United States Department of Justice. Its responsibilities include the investigation and prevent ...

has ruled that since the sound waves are not dampened and are metered at the same levels at two measuring points ( to the left and 0 m in front of the muzzle and left and forward of the muzzle) this is not a sound suppressing device. The only action which a muzzle shroud performs is shielding the area directly behind the muzzle from the worst blast pressures.

Muzzle brake A muzzle brake or recoil compensator is a device connected to, or a feature integral to the construction of, the muzzle or barrel of a firearm or cannon that is intended to redirect a portion of propellant gases to counter recoil and unwant ...

s direct the escaping gases rearward toward the shooter, thus increasing blast pressure directed toward the operator's ears. The same principle that lessens felt recoil also acts to enhance the sound levels reaching the shooter. Some of the muzzle brakes designed for heavy-caliber rifles ( .338 Lapua, .408 CheyTac, .50 BMG) incorporate "blast shields" projecting laterally from the sides of the muzzle crown. These reflect sound waves traveling rearward via the muzzle brake blast chambers. These small leaves, however, do not fully enclose the muzzle diameter, and so block only the worst blast path, while allowing the majority of escaping gases to circumvent the shield by traveling around them, still reaching the shooter's ears, potentially causing hearing damage.

Gallery

Digital Museum MG 34 Right.jpg, An

MG 34 The MG 34 (shortened from German: ''Maschinengewehr 34'', or "machine gun 34") is a German recoil-operated air-cooled general-purpose machine gun, first tested in 1929, introduced in 1934, and issued to units in 1936. It introduced an entirely n ...

with a conical muzzle shroud. YM-battlefield-Lee-Enfield-2.jpg, The Lee Enfield

Jungle Carbine The Rifle No. 5 Mk I, was a derivative of the British Lee–Enfield No. 4 Mk I,Wilson (2006) Following experience of jungle fighting in the Pacific War, the British came to "the conclusion that a rifle shorter and lighter than the standard issue ...

(Rifle No. 5 Mk I) with a conical flash suppressor (muzzle shroud). Peter Worsley, Australian paralympic shooter.jpg, Front sight extensions on an ISSF air rifle are effectively muzzle shrouds used to increase the sight radius, aiding in precise aiming with

iron sights Iron sights are a system of physical alignment markers (usually made of metallic material) used as a sighting device to assist the accurate aiming of ranged weapons (such as a firearm, airgun, crossbow or even compound bow), or less commonly as ...

. Letecké muzeum Kbely (9).jpg, A Lewis gun with a muzzle shroud.

References