Sten submachine gun

The STEN (or Sten gun) was a family of British submachine guns chambered in 9×19mm and used extensively by British and Commonwealth forces throughout World War II and the Korean War. They were notable for having a simple design and very low production cost making them effective insurgency weapons for resistance groups.

STEN is an acronym, from the names of the weapon's chief designers, Major Reginald V. Shepherd and Harold Turpin, and EN for Enfield. Over 4 million Stens in various versions were made in the 1940s.

Sten submachine gun
Class Manportable
Type Machine Guns
Manufacturer Royal Small Arms Factory
Origin United Kingdom - UK (Great Britain)
Country Name Origin Year
United Kingdom - UK (Great Britain) 1941
Country Name Operational Year Retirement Year
China 1937 1945 View
China 1962 1962 View
Cyprus 1974 1974 View
Egypt 1956 1956 View
Indonesia 1945 1949 View
Ireland 1956 1962 View
Ireland 1968 1998 View
Kenya 1952 1960 View
Korea 1950 1953 View
Laos 1953 1975 View
Malaysia 1948 1960 View
Palestine 1948 1949 View
Poland 1944 1944 View
United Kingdom - UK (Great Britain) 1939 1945 View
Vietnam 1946 1954 View
Vietnam 1955 1975 View
Zimbabwe (Rhodesia) 1964 1979 View
ManufacturerName Production From Production To Quantity
Royal Small Arms Factory View
The Sten was a blowback-operated submachine gun firing from an open bolt with a fixed firing pin on the face of the bolt. This means the bolt remains to the rear when the weapon is cocked, and on pulling the trigger the bolt flies forward under spring pressure, stripping the round from the magazine, chambering it and firing the weapon all in the same movement. There is no breech locking mechanism, the rearward movement of the bolt caused by the recoil impulse is arrested only by the mainspring and the bolt's inertia. The basic operating principles were similar to those of the German MP40, Russian PPSh-41, US M3 submachine gun and numerous other designs. These shared similar attributes and faults; they were simple and cheap to manufacture, and put an automatic weapon into the hands of soldiers, greatly increasing the short-range firepower of the infantry, especially when the main infantry weapon was a bolt-action rifle capable of only around 15 rounds per minute and not suited for short-range combat. However, the open-bolt firing and use of pistol ammunition severely restricted accuracy, with an effective range of around 100m.

Stoppages could occur due to a variety of problems: some as a result of poor maintenance, while others were particular to the Sten. Carbon buildup on the face of the breech or debris in the bolt raceway could cause a failure to fire, while a dirty chamber could cause a failure to feed. Firing the Sten by grasping the magazine with the supporting hand tended to wear the magazine catch, altering the angle of feed and causing a failure to feed - the correct method of holding the weapon was as with a rifle, the left hand cradling the fore piece, as per the picture of Mr. Churchill firing one below.

Additional problems stemmed from the Sten's magazine, which was a direct copy of the one used in the German MP-38, originally in order to facilitate the use of German 9 mm magazines. Unfortunately, this decision necessarily incorporated the Erma magazine's faults in the process. The magazine had two columns of 9 mm cartridges in a staggered arrangement, merging at the top to form a single column. While other staggered magazines, such as the Thompson, fed from both the left and right side alternately (double-column, double feed), the Sten magazine, like the MP38, required the cartridges to gradually merge at the top of the magazine to form a single column (double column, single feed). As a consequence, any dirt or foreign matter in this taper area could cause feed malfunctions. Additionally, the walls of the magazine lip had to endure the full stresses of the rounds being pushed in by the spring. This, along with rough handling could result in deformation of the magazine lips (which required a precise 8° feed angle to operate), resulting in misfeeding and a failure to fire.

Modern 9 mm magazines, such as those used by the Sterling SMG, are curved and feed both sides to avoid this problem. If a Sten failed to feed due to jammed cartridges in the magazine, standard practice to clear it was as follows: remove magazine from Sten, tap the base of the magazine against the knee, re-insert magazine in Sten, then recocking the weapon and firing again as normal. To facilitate easier loading when attempting to push the cartridges down to insert the next one, a magazine filler tool was developed and formed part of the weapon's kit.

The slot on the side of the body where the cocking knob ran was also a target of criticism, as the long opening could allow foreign objects to enter. On the other hand, a beneficial side-effect of the Sten's minimalist design was that it would fire without any lubrication. This proved useful in desert environments such as the Western Desert Campaign, where oil attracted and retained dust and sand.

The open bolt design combined with cheap manufacture and rudimentary safety devices also meant the weapon was prone to accidental discharges, which proved hazardous. A simple safety could be engaged while the bolt was in the rearwards (cocked) position. However, if a Sten with a loaded magazine, with the bolt in the closed position, was dropped or the butt was knocked against the ground, the bolt could move far enough rearward to pick up a round (but not far enough to be engaged by the trigger mechanism) and the spring pressure could be enough to chamber and fire the round. The Mk 4 cocking handle was designed to prevent this by enabling the bolt to be locked in its forward position, thereby immobilising it. Wear and manufacturing tolerances could render these safety devices ineffective.

The Sten emerged while Britain was engaged in the Battle of Britain, facing invasion by Germany. The army was forced to replace weapons lost during the evacuation from Dunkirk while expanding at the same time. Prior to 1941 (and even later) the British were purchasing all the Thompson submachine guns they could from the United States, but these did not begin to meet demand. The American entry into the war at the end of 1941 placed an even bigger demand on the facilities making Thompsons. In order to rapidly equip a sufficient fighting force to counter the Axis threat, the Royal Small Arms Factory, Enfield, was commissioned to produce an alternative.

The credited designers were Major R. V. Shepherd, OBE, Inspector of Armaments in the Ministry of Supply Design Department at The Royal Arsenal, Woolwich, (later Assistant Chief Superintendent at the Armaments Design Department) and Mr. Harold John Turpin, Senior Draughtsman of the Design Department of the Royal Small Arms Factory (RSAF), Enfield. Shepherd had been recalled to service after having retired and spending some time at BSA.

The Sten shared design features, such as its side-mounted magazine configuration, with the Royal Navy's Lanchester submachine gun, which was a copy of the German MP28. In terms of manufacture, the Lanchester was entirely different, being made of high-quality materials with pre-war fit and finish, in stark contrast to the Sten's austere execution. The Lanchester and Sten magazines were even interchangeable (though the Lanchester's magazine was longer with a 50-round capacity, compared to the Sten's 32-round capacity).

The Sten used simple stamped metal components and minor welding, which required a minimum of machining and manufacturing. Much of the production could be performed by small workshops, with the firearms assembled at the Enfield site. Over the period of manufacture the Sten design was further simplified: the most basic model, the Mark III, could be produced from five man-hours work. Some of the cheapest versions were made from only 47 different parts. It was distinctive for its bare appearance (just a pipe with a metal loop for a stock), and its horizontal magazine. The Mark I was a more finely finished weapon with a wooden foregrip and handle; later versions were generally more spartan, although the final version, the Mark V, which was produced after the threat of invasion had died down, was produced to a higher standard.

The Sten underwent various design improvements over the course of the war. For example, the Mark 4 cocking handle and corresponding hole drilled in the receiver were created to lock the bolt in the closed position to reduce the likelihood of accidental discharges inherent in the design. Most changes to the production process were more subtle, designed to give greater ease of manufacture and increased reliability. Build quality ranged from quite good (Canadian production) to poor (early British production.) Sten guns of late 1942 and beyond were, in general, highly effective weapons, though complaints of accidental discharge continued throughout the war. Such was the ease of manufacture that the Germans also produced a version of the Sten, the MP 3008, late in the war and the Sten was used extensively by Jewish partisans during the Israeli War of Independence.

The Sten was replaced by the Sterling submachine gun from 1953 and was gradually withdrawn from British service in the 1960s. The other Commonwealth nations made or adopted their own replacements.

Variants

  • Mark I
  • Mark I*
  • Mark II
  • Mark II (Canadian)
  • Mark III
  • Mark V
  • Mark VI
  • Suppressed models
  • Mk IIS
  • Mk VI
Experimental models

  • Mark II (wooden butt model)
  • Mark II (Rosciszewski model)
  • Mark II (pistol grip model)
  • Model T42
  • Mark III (wooden model)
  • Mark III (wooden model II)
  • Mark IV
  • Rofsten
Foreign-built variants and post 1945 derivatives

  • Argentine Sten
  • Palestininian Mandate Stens
  • French Sten
  • Norwegian Sten
  • Danish Sten
  • Polish Sten
  • Gerät Potsdam
  • MP 3008
  • Austen Mk I
  • Imperia submachine gun
  • Sputter Gun
  • Halcon ML-57
  • Cellini Dunn SM-9
  • International Ordnance MP2
  • Pleter 91
  • SaskSten

The Sten, especially the Mark II, tended to attract affection and loathing in equal measure. Its peculiar appearance when compared to other firearms of the era, combined with sometimes questionable reliability made it unpopular with some front-line troops. It gained nicknames such as "Plumber's Nightmare", "Plumber's Abortion", or "Stench Gun". The Sten's advantage was its ease of mass-production manufacture in a time of shortage during a major conflict.

Made by a variety of manufacturers, often with subcontracted parts, some early Sten guns were made poorly and/or not made to specification, and could malfunction in operation, sometimes in combat. The double-column, single-feed magazine copied from the German MP28 was never completely satisfactory, and hasty manufacturing processes often exacerbated misfeed problems inherent in the design. A common statement heard from British forces at the time was that the Sten was made "by Marks and Spencer out of Woolworth." British and Commonwealth forces in the early years of the war often extensively test-fired their weapons in training to weed out bad examples; a last-minute issue of newly manufactured Stens prior to going into action was not always welcomed.

The MK II and MK III Stens were regarded by many soldiers as very temperamental, and could accidentally discharge if dropped or even laid on the ground whilst the gun was cocked. Others would fire full-automatic when placed on 'single', or fire single shots when placed on 'automatic'. This was particularly true of early Stens using bronze bolts, where the sear projection underneath the bolt could wear down more easily than ones made of case-hardened steel.

Stens could jam at inopportune moments. One of the more notable instances of this was the assassination of SS-Obergruppenführer Reinhard Heydrich on 27 May 1942, when a Czechoslovak soldier – Warrant Officer Jozef Gabcík – fired his Sten point blank at Heydrich, only to have it misfire. His comrade Jan Kubiš then hastily tossed a grenade, which mortally wounded Heydrich. There are other accounts of the Sten's unreliability, some of them true, some exaggerated and some which are apocryphal. France manufactured (well-made) Sten copies postwar into the early 1950s, evidently believing in the basic reliability and durability of the design.

A well-maintained (and properly-functioning) Sten gun was a devastating close-range weapon for sections previously armed only with bolt-action rifles. In addition to regular British and Commonwealth military service, Stens were air-dropped in quantity to resistance fighters and partisans throughout occupied Europe. Due to their slim profile and ease of disassembly/reassembly, they were good for concealment and guerrilla warfare. Wrapping the barrel in wet rags would delay undesirable overheating of the barrel Guerrilla fighters in Europe became adept at repairing, modifying and eventually scratch-building clones of the Sten (over 2,000 Stens and about 500 of the similar Blyskawica SMGs were manufactured in occupied Poland).

Canadian infantry battalions in northwest Europe retained spare Sten guns for special missions and the Canadian Army reported a surplus of the weapons in 1944. The Sten saw use even after the economic crunch of World War II, replacing the Royal Navy's Lanchester submachine guns into the 1960s, and was used in the Korean War, including specialist versions for British Commandos. It was slowly withdrawn from British Army service in the 1960s and replaced by the Sterling SMG; Canada also phased out Sten, replacing it with the C1 SMG.

The Sten was one of the few weapons that the State of Israel could produce domestically during the 1948 Arab–Israeli War. Even before the declaration of the State of Israel, the Yishuv had been producing Stens for the Haganah; after the declaration, Israel continued making Stens for IDF use. The opposing side also used (mostly British-made) Stens, particularly the irregular and semi-regular Arab Liberation Army.

In the 1950s "L numbering" came into use in the British Army for weapons—Stens were then known as L50 (Mk II), L51 (Mk III) and L52 (Mk V).

One of the last times the Sten was used in combat during British service was with the RUC during the IRA border campaign of 1956–1962. In foreign service, the Sten was used in combat at least as recently as the Indo-Pakistani War of 1971.

In 1971 various marks of Stens were used by guerilla fighters during the Bangladesh Liberation War.

A number of suppressed Stens were in limited use by the US Special Forces during the Vietnam war, including c. 1971, by the United States Army Rangers

In 1984, Indian prime minister Indira Gandhi was assassinated by two of her bodyguards, one of whom fired the entire magazine of his Sten at point-blank range.

In the Second Sino-Japanese War and the Chinese Civil War, both nationalists and communists used the Sten. Some Stens were converted by the communists to 7.62×25mm by using the magazine housing from a PPS to accept curved PPS magazines. An example of such a conversion is on display at the Imperial War Museum, London.

The Finnish Army acquired moderate numbers of Stens in the late 1950s, mainly Mk. III versions. Refurbishment at the Kuopio Arsenal included bluing of the arms. Stens in Finnish service saw limited usage by conscripts (notably combat swimmers) and were mostly stockpiled for use in a future mobilization.

During the Zapatista movement in 1994 some Zapatista soldiers were armed with Sten guns.

Type Submachine gun
Place of origin United Kingdom
Service history
In service 1941–1960s
Used by Argentina, Albania, Australia, Bangladesh, Belgium, Canada, Ceylon, Cyprus, People's Republic of China, Denmark, Finland, France, Greece, India, Indonesia, Israel, Italy, Japan, Jordan, Kenya, Luxembourg, Malaysia, Malta, Netherlands, Nazi Germany, New Zealand, Nigeria, Norway, Pakistan, Poland, Rhodesia / Rhodesia, South Africa, North Vietnam, outh Vietnam, Turkey, United Kingdom, United States, Yugoslavia
Wars World War II

Warsaw Uprising

Second Sino-Japanese War

Chinese Civil War

Indonesian National Revolution

Malayan Emergency

Korean War

Mau Mau Uprising

Suez Crisis

1948 Arab-Israeli War

Sino-Indian War

First Indochina War

Vietnam War

Laotian Civil War

Rhodesian Bush War

Turkish invasion of Cyprus

Indo-Pakistan Wars

IRA Border Campaign

The Troubles

British colonial conflicts
Production history
Designer Major Reginald V. Shepherd
Harold J. Turpin
Designed 1940
Manufacturer Royal Small Arms Factory

Enfield

BSA

ROF Fazakerley

ROF Maltby

ROF Theale

Berkshire

Lines Brothers Ltd

Long Branch Canada (plus numerous sub-contractors making individual parts).

Various Underground Resistance Group Factories.
Produced 1941– (version dependent)
Number built 3.7–4.6 million (all variants, depending on source)
Variants Mk. I, II, IIS, III, IV, V, VI

Unit Cost $10 or £2.3 in 1942
Weight 3.2 kg (7.1 lb) (Mk. II)
Length 760 mm (30 in)
Barrel length 196 mm (7.7 in)
Cartridge 9×19mm Parabellum
Action Blowback-operated, Open bolt
Rate of fire version dependent; ~500-round/min
Muzzle velocity 365 m/s (1,198 ft/s)

305 m/s (1,001 ft/s) (suppressed models)
Effective firing range 100 m
Feed system 32-round detachable box magazine
Sights fixed peep rear, post front

End notes