Heckler & Koch’s Suppressed MP5 Is Only as Loud as a Shout
Built-in suppressor keeps down the noise
by MATTHEW MOSS
In the early 1970s, Heckler & Koch began work on an integrally-suppressed variant of its extremely popular roller-delayed blowback submachine gun, the MP5. The company designated the new suppressed weapon the MP5SD, “SD” meaning Schalldämpfer or “sound suppressor.”
While all MP5s could be fitted with an external suppressor using the quick-detachable tri-lug system, this compromised the handiness of the weapon. With this in mind, H&K decided to develop a dedicated variant. The firm introduced the MP5SD in 1974. It boasts an integral suppressor and includes several other changes — such as a lighter bolt — to ensure reliable cycling.
In 1964 Walther, one of H&K’s main rivals, developed its own suppressors for its MPK submachine gun and P38 pistols. Walther was the first German arms-manufacturer to be granted a special permit for suppressor production. The MPK’s barrel configuration allows the suppressor to be used without impeding the weapon’s sights. These equipped West German intelligence agents — and may also have been issued to U.S. Special Forces stationed in Western Germany.
Unlike Walther’s add-on suppressor, the MP5SD’s integral suppressor minimizes additional length. The MP5SD’s suppressor is aluminum, which helps to keep down its weight and retain the weapon’s previous balance.
The SD’s short barrel featured 30 2.5-millimeter ports in order to bleed off a significant amount of the propellant gases into the expansion chamber of the suppressor. This allows the volume of the gas to expand — and the pressure to drop — before the gas passes through the second chamber, which contains conical baffles and further reduces the weapon’s report.
The MP5SD’s barrel-and-suppressor combination cuts the speed of the round to subsonic velocity. The suppressor reduces peak muzzle noise to approximately 70 decibels, roughly the same intensity as a loud human voice.
One drawback of H&K’s early SD design was carbon build-up inside the suppressor housing and on the barrel, which — without regularly cleaning — would cause the suppressor to lock up.
The MP5SD quickly gained favor with tier-one special forces units, such as the British Special Air Service and Special Boat Service, U.S. Army Delta Force and the U.S. Navy SEALs — and has been adopted by military and security forces around the world.
Not only does the suppressor reduce the sound of the weapon, it also dissipates muzzle flash. Since its launch in the mid-1970s there have been six incarnations of the SD with various stock setups and trigger groups. The MP5SD continues to be popular with militaries and police forces around the world.
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