Great Firearms: The Heckler & Koch MP5-SD Suppressed 9mm

In the world of military and law enforcement operations, the submachine gun has a special place in the hearts of operators.  A compact, reliable weapon firing pistol caliber ammunition at a high-cyclic rate is exceedingly useful for their types of close-quarter, in-your-face combat that they experience in their day-to-day training and deployment.  While there are numerous designs of submachine gun, there is one design that stands out above all others and has stood the test of time.  That is the Heckler and Koch MP5. 

The MP-5 SD 9mm

The H&K MP5 (which stands for machinenpistole 5 or “machine pistol model 5”) is a selective-fire delayed blowback submachine gun which utilizes the NATO standard 9mm Parabellum pistol cartridge.  Developed in 1964 and released to the German Federal Police in 1966, it quickly became the most widely used submachine gun by the worlds counter terrorist and special operations forces as well as those countries in the newly formed NATO alliance.  It used plentiful 9mm Parabellum ammunition, and was very controllable, even on fully automatic.  This use of common ammunition simplified logistics and the performance of the weapon allowed for a high level of precision for the tactical operators that used them. 

Design Specs for the Roller Locking Mechanism from the U.S. Patent Office

The MP5 uses a type of delayed blowback system as its operating mechanism.  This system, pioneered in the dark days of the Nazi regime in World War Two, utilizes two rollers attached to the bolt carrier inside of the weapon.  Firing from a closed bolt, the rollers on either side of the bolt carrier fit into recesses in the chamber of the weapon, delaying the opening of the bolt and extraction of the spent cartridge until the bullet has left the barrel and the pressures inside the chamber have dropped to a safe level.  The MP5 also utilized a fluted chamber, with shallow flutes inside the chamber that allowed gasses to “lubricate” the cartridge case and prevent it from expanding and sticking to the chamber walls.  These two systems were carried over from H&K’s extremely successful and reliable 7.62x51mm rifle, the G3.  These two systems greatly contributed to the reliability of the weapon and helped to ensure its place in the hands of military forces around the globe.

Standard MP-5 in Unsuppressed Configuration

In 1974, H&K designed a integrally suppressed variant of the MP5, called the MP5-SD.  It utilized a large suppressor that slipped over almost the entire length of the barrel.  Just forward of the threading that the suppressor used to attach itself to the receiver, are 30 gas ports.  These ports are designed to release the propellant gasses into the suppressor, which serves two functions; first, it slows the acceleration of the bullet to subsonic velocity, thereby decreasing or eliminating the supersonic crack of the bullet downrange. Secondly, it allows the gasses escaping the firearm to slow to a subsonic level so they do not produce the characteristic crack of a gunshot when the bullet exits the barrel.  When combined, these ports and suppressor result in a very mild report, one that sounds remarkably like a loud cough.

My experiences with the MP5-SD have been extremely positive.  My shooting buddy has a semi-automatic variant with collapsible stock in 9mm Parabellum caliber and it is an extremely effective weapon out to 100 yards.  The report is very mild, and hearing protection is optional when firing the MP5-SD.  While the suppressor is designed to reduce normal supersonic ammunition to subsonic velocities, I’ve found that the suppressor works best when using 147 grain subsonic 9x19mm ammunition. The only caveat I have found is to not use +P ammunition in the MP-5, as the higher pressure 9mm +P ammo will cause the bolt to open before chamber pressures have dropped to a safe level, thereby risking damage to the firearm and/or shooter.

The MP5-SD is truly an iconic submachine gun, and the MP5 and its variants have figured in thousands of special operations performed by the world’s militaries.  In my limited experience, I have found the reputation of the MP5 to be well deserved as it is a reliable and well-designed weapons system that will perform well and be around for years to come.