A HK416 14.5" with a suppressor (Picture: US Department of Defense).
By David Hambling, technology expert
Suppressors, often misleadingly called ‘silencers,’ reduce the flash and noise made by a gunshot.
In movies, suppressors are tiny and make weapons practically inaudible.
However, in real life, a rifle suppressor may add 30 cm, and a shot still makes a substantial, if greatly reduced, report.
Suppressors are becoming increasingly common, especially in urban battlegrounds, and even heavy weapons are now becoming available in ‘stealth’ versions.
The British Army carried out trials with suppressors as part of the three-year Platoon Combat Experiment (PCE).
Much of the noise of a shot comes from the hot combustion gases expanding in the open air – pretty much the same effect as a champagne cork popping.
As part of the PCE, bespoke suppressors were issued for every weapon in the Burma Company of The Duke of Lancaster’s Regiment (1 LANCS), including light and general-purpose machine guns.
The aim was to reduce noise-induced hearing loss, which had been identified as a problem - unsurprisingly, the main contributor was the noise from firing weapons.
In the PCE tests, suppressors were effective for personal weapons including the L85 rifle but suffered from overheating on machine-guns used for sustained fire.
There are no plans yet to roll out suppressed weapons on a larger scale, but the project also highlighted the tactical advantages of suppressors, and work continues in this area.
Others are already making increased used of suppressed weapons. A study this summer noted numerous occasions when both ISIS forces and their Kurdish YPG opponents have deployed them.
Sometimes suppressed weapons were used when attacking an outpost or a group of sentries, to reduce the chances of alerting other forces nearby.
Suppressors also have a considerable morale effect: there is something frightening about an opponent who can strike without being seen or heard.
But the biggest advantage of suppressors is the edge they give in a firefight.
Retired Army Major General and Vietnam veteran Robert Scales pointed out how much soldiers rely on sound to locate their opponent: “There are virtually no instances where an ambushed unit actually sees the enemy.
"Both sides shoot at flashes and sounds."
Suppressors reduce both the noise and the muzzle flash, making ambushers extremely difficult to locate, especially in darkness.
This is why both the US Army and Marine Corps are looking at a new generation of suppressed weapons for battlefield use, and have bought trial batches of suppressors for their M-4 carbines.
Perhaps the most advanced work in this area can be found in Russia. Rather than simply adding a suppressor to an existing weapon, they redesigned a rifle from scratch.
A suppressor may reduce the speed of escaping gas, but some noise remains; instead the Russians use special ‘captive piston’ ammunition.
The exhaust gases remain trapped inside the cartridge case, and the bullet is propelled by a piston.
This type of ammunition, first used in an assassination pistol developed for the KGB and GRU in the 1970s, is expensive but very quiet; the sound is described as a ‘pop’ rather than a ’bang.’
The captive-piston approach also ensures that firing is smokeless, and because there is no external suppressor, it does not add to the length of the weapon.
Even with no gas exhaust, the bullet itself makes a noise. A bullet travelling faster than the speed of sound produces a type of sonic boom which has been described as “the loud tearing of a bedsheet,” and can help locate the firer.
To be as quiet as possible you need to slow the bullet down to subsonic speed, which reduces its range and impact power.
Last summer the Russians unveiled a new a silenced sniper rifle, firing a captive-piston round, based on the existing the MTs-116M.
This compensates for its low muzzle velocity with a massive 12.7mm bullet, ten times as heavy as the 5.56mm bullets fired by the British Army’s L85.
In spite of its slow speed, the heavy round will pierce any known body armour at 200 metres.
The Russians are also developing heavier silenced weapons.
The 2B25 is a silenced 82mm medium mortar, made by Russian arms manufacturer Rostec, again with special ammunition based on the same captive-piston design.
It has a shorter range than most mortars, launching a high explosive-fragmentation bomb to just over a kilometre. However, according to the makers, it produces almost no muzzle flash or smoke.
The firing sound is as quiet as an AK-47 fitted with a suppressor. Several dozen of the mortars have reportedly been delivered to Russian Special Forces units.
In theory, this type of weapon would allow attackers to rain down mortar bombs on an opponent without giving away their position: with no flash, bang or smoke, the mortars would be extremely difficult to locate.
Suppressed weapons cannot match the range and effectiveness of noisier, more conventional designs.
But in the close-quarter battle, ‘silent but deadly’ suppressed weapons may increasingly turn out to be a trump card.