Additional Umarex MP5K-PDW Photos

History behind the firearm that inspired the Umarex MP5K Air Gun

The MP5 is one of the most widely used submachine guns in the world, having been adopted by 40 nations and numerous military, law enforcement, intelligence, and security organizations. It is widely used by SWAT teams in North America. In 1999, Heckler & Koch developed the Heckler & Koch UMP, the MP5's successor; both are currently available. There are over 100 variants of the MP5, including some semi-automatic versions.

Development

Work on the MP5 began in 1964 and two years later it was adopted by the German Federal Police, border guard and army special forces. In 1980, the MP5 achieved iconic status as a result of its use on live television by SAS commandos in Operation Nimrod, where they stormed the Iranian Embassy in London, rescuing hostages and killing five terrorists. The MP5 became a mainstay of SWAT units of law enforcement agencies in the United States since then. However, in the late 1990s, as a result of the North Hollywood shootout, police special response teams have supplanted some MP5s with AR-15-based assault rifles.

Heckler & Koch MP5A2

The primary version of the MP5 family is the MP5A2, which is a lightweight, air-cooled, selective fire delayed blowback operated 9x9mm Parabellum weapon with a roller-delayed bolt. It fires from a closed bolt (bolt forward) position. The fixed, free floating, cold hammer-forged barrel has 6 right-hand grooves with a 1 in 250 mm (1:10 in) rifling twist rate and is pressed and pinned into the receiver. The first MP5 models used a double-column straight box magazine, but since 1977, slightly curved, steel magazines are used with a 15-round capacity (weighing 0.12 kg) or a 30-round capacity (0.17 kg empty).

Heckler & Koch MP5K

In 1976 a shortened version of the MP5A2 was introduced; the MP5K (K from the German word Kurz = "short") was designed for close quarters battle use by clandestine operations and special services. The MP5K does not have a shoulder stock (the receiver end was covered with a flat end cap, featuring a buffer on the inside and a sling loop on the outside), and the bolt and receiver were shortened at the rear. The resultant lighter bolt led to a higher rate of fire than the standard MP5. The barrel, cocking handle and its cover were shortened and a vertical foregrip was used to replace the standard handguard. The barrel ends at the base of the front sight, which prevents the use of any sort of muzzle device. A civilian semiautomatic derivative of the MP5K known as the SP89 was produced that had a foregrip with a muzzle guard in place of the vertical grip.

Heckler & Koch MP5K-PDW

In 1991 a further variant of the MP5K was developed, designated the MP5K-PDW (PDW) �Personal Defense Weapon) that retained the compact dimensions of the MP5K but restored the fire handling characteristics of the full-size MP5A2. The MP5K-PDW uses a side-folding synthetic shoulder stock (made by the U.S. company Choate Machine and Tool), a "Navy" trigger group, a front sight post with a built-in tritium insert and a slightly lengthened threaded, three-lug barrel (analogous to the MP5-N). The stock can be removed and replaced with a receiver endplate; a rotary drum with apertures from the MP5A2 can also be used.

Inovative Sights

The adjustable iron sights (closed type) consist of a rotating rear diopter drum and a front post installed in a hooded ring. The rear sight is adjustable for both windage and elevation with the use of a special tool, being adjusted at the factory for firing at 25m with standard 124 grains FMJ �19mm NATO ammunition; the drum provides four different apertures of varying width used to adjust the light entrance in the diopter system, according to the user's eye relief and tactical situation.

Trigger and Selector

The MP5 has a hammer firing mechanism. The trigger group is housed inside an interchangeable polymer trigger module (with an integrated pistol grip) and equipped with a three-position fire mode selector that serves as the manual safety toggle. The "S" or Sicher position in white denotes weapon safe, "E" or Einzelfeuer in red represents single fire, and "F" or Feuersto� (also marked in red) designates continuous fire. The SEF symbols appear on both sides of the plastic trigger group.

The selector lever is actuated with the thumb of the shooting hand and is located only on the left side of the original SEF trigger group or on both sides of the ambidextrous trigger groups. The safety/selector is rotated into the various firing settings or safety position by depressing the tail end of the lever. Tactile clicks (stops) are present at each position to provide a positive stop and prevent inadvertent rotation. The "safe" setting disables the trigger by blocking the hammer release with a solid section of the safety axle located inside the trigger housing.

The non-reciprocating cocking handle is located above the handguard and protrudes from the cocking handle tube at approximately a 45 angle. This rigid control is attached to a tubular piece within the cocking lever housing called the cocking lever support, which in turn, makes contact with the forward extension of the bolt group. It is not however connected to the bolt carrier and therefore cannot be used as a forward assist to fully seat the bolt group. The cocking handle is held in a forward position by a spring detent located in the front end of the cocking lever support which engages in the cocking lever housing. The lever is locked back by pulling it fully to the rear and rotating it slightly clockwise where it can be hooked into an indent in the cocking lever tube.

Operating Mechanism

The roller-delayed blowback mechanism originated from the aborted StG 45(M) assault rifle prototypes developed in Nazi Germany at the end of World War II. The bolt rigidly engages the barrel extension��a cylindrical component welded to the receiver into which the barrel is pinned. The delay mechanism is of the same design as that used in the G3 rifle. The two-part bolt consists of a bolt head with rollers and a bolt carrier. The heavier bolt carrier lies up against the bolt head when the weapon is ready to fire and inclined planes on the front locking piece lie between the rollers and force them out into recesses in the barrel extension.

When fired, expanding propellant gases produced from the burning powder in the cartridge exert rearward pressure on the bolt head transferred through the base of the cartridge case as it is propelled out of the chamber. A portion of this force is transmitted through the rollers projecting from the bolt head, which are cammed inward against the inclined flanks of the locking recesses in the barrel extension and to the angled shoulders of the locking piece. The selected angles of the recesses and the incline on the locking piece produce a velocity ratio of about 4:1 between the bolt carrier and the bolt head. This results in a calculated delay, allowing the projectile to exit the barrel and gas pressure to drop to a safe level before the case is extracted from the chamber.