An Cosantóir

An Cosantóir October 2019 www.dfmagazine.ie 30 | BY DEFENCE FORCES ORDNANCE OFFICER C ommonly referred to as silencers, mufflers or sound moderators, a suppressor is a device used to moderate the sound of a weapon when fired. To understand how suppressors work, one must first understand what causes the sound heard when a projectile is fired. Sound can be defined as varia- tions in the pressure, temperature and density of the medium through which the sound waves move, for example air or water. When a weapon's trigger is pressed, it results in a chain reac- tion that leads to a round or rounds being fired. Pressure on the trigger releases the firing pin, which strikes the cartridge's primer, igniting and combusting the powder inside the round, driving the bullet out through the barrel, with the gases and unburned propellants follow- ing it causing muzzle blast. If the speed of the bullet exceeds the speed of sound, a ballistic N-shaped wave is produced along with the muzzle blast. These sounds to- gether are known as the gunshot. The sound level of the muzzle blast is strongest in the direction the barrel is facing. However, noise is still detected in the vicinity of the shooter, due to sound waves re- flecting off the ground and nearby surfaces. Muzzle blast, the loudest sound caused by firing a small arms weapon, is affected by factors such as the environment, ammunition and calibre of the weapon. Ear muffs and ear plugs can be used to distort sound during training and military operations but these affect the shooter's ability to hear sound around them. Suppressors provide an alternate method to reduce this problem. Weapon suppressors can mi- nimise muzzle blast by breaking up the initial wave front from the gases, disturbing the shock waves as they pass through a series of baffles in the mechanism of the suppressor. Metals, such as steel, aluminium or titanium, are used in the con- struction of suppressors as they must be capable of enduring high pressure as well as being heat resistant. Suppressors divert gas flow and prohibit gas from flowing freely with structures called baffles and spacers. Wired mesh with re- flective discs and surfaces are also included as structural components. Suppressors are usually cylindri- cal and attached to the muzzle of a weapon such as a pistol or rifle. Expansion chambers allow the barrel to release gases into them and lower the muzzle blast effect. Suppressors also reduce the noise by decelerating and rapidly cool- ing the expanding gases released when a round is fired. There are at least four chambers in a suppres- sor, with the largest located near the muzzle end, as this allows unburned propellant and gas to expand substantially and slow down before coming into contact with the baffles, which in turn absorb a lot of heat before the gas and unburnt propellant exit the weapon. A suppressor also increases the volume of a barrel by 20 times or more, allowing the gas behind the bullet more space to expand and lowering its pressure before the bullet exits the barrel. This causes a reduced sound wave. Suppressors have many advan- tages, including allowing easier communication between soldiers during live fire exercises and opera- tions; improving shot accuracy by promoting barrel stabilization; elim- inating muzzle flash and preventing the blooming of night vision equip- ment; hiding a shooter's location from the enemy; and reducing recoil and muzzle flip, helping with the accuracy of subsequent shots. This topic is one of many taught in detail during the MAMF Techni- cians Course and the Light Weapon Systems Engineering block of the Ordnance Young Officers Course. A thorough understanding of how light weapons work allows the Ord- nance Corps to fully support Óglaigh na hÉireann at home and abroad.

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