MDScorpio shooting the MP5SD
In 1974 H&K initiated design work on a sound-suppressed variant of the MP5, designated the MP5SD (SD – Schalldämpfer German for "sound dampened"), which features an integral but detachable aluminum sound suppressor and a lightweight bolt. The weapon's 146 mm (5.7 in) barrel has 30 2.5 mm (0.1 in) ports drilled forward of the chamber through which escaping gases are diverted to the surrounding sealed tubular casing that is screwed on to threading on the barrel’s external surface just prior to the ported segment. The suppressor itself is divided into two stages; the initial segment surrounding the ported barrel serves as an expansion chamber for the propellant gases, reducing gas pressure to slow down the acceleration of the projectile. The second, decompression stage occupies the remaining length of the suppressor tube and contains a stamped metal helix separator with several compartments which increase the gas volume and decrease its temperature, deflecting the gases as they exit the muzzle, so muffling the exit report. The bullet leaves the muzzle at subsonic velocity, so it does not generate a sonic shock wave in flight. As a result of reducing the barrel’s length and venting propellant gases into the suppressor, the bullet’s muzzle velocity was lowered anywhere from 16% to 26% (depending on the ammunition used) while maintaining the weapon’s automation and reliability. The weapon was designed to be used with standard supersonic ammunition with the suppressor on at all times.
The MP5SD is produced exclusively by H&K in several versions: the MP5SD1 and MP5SD4 (both have a receiver end cap instead of a buttstock), MP5SD2 and MP5SD5 (equipped with a fixed synthetic buttstock) and the MP5SD3 and MP5SD6 (fitted with a collapsible metal stock). The MP5SD1, MP5SD2 and MP5SD3 use a standard "SEF" trigger group (from the MP5A2 and MP5A3), while the MP5SD4, MP5SD5 and MP5SD6 – a trigger module with a mechanically limited 3-round burst mode and ambidextrous selector controls (from the MP5A4 and MP5A5). A suppressed version was also produced for the U.S. Navy - designated the MP5SD-N, which is a version of the MP5SD3 with a retractable metal stock, front sight post with tritium-illuminated dot and a stainless steel suppressor. This model has a modified cocking handle support to account for the slightly larger outside diameter of the suppressor. The design of the suppressor allows the weapon to be fired with water inside, should water enter the device during operation in or near water.
|Liveleak on Facebook|