Carbine, Machine, Sten
Sten Mk. IIS (Suppressed version)
Type	Submachine gun
Place of origin	United Kingdom
Service history
In service	1941–1960s
Used by	United Kingdom, Commonwealth, Norway, Free French, Partisans and various others
Wars	World War II, Korean War, Mau Mau Uprising, Suez Crisis, 1948 Arab-Israeli War, Sino-Indian War, Indo-Pakistan Wars
Production history
Designer	Major Reginald V. Shepherd Harold J. Turpin
Designed	1940
Manufacturer	Royal Small Arms Factory, Enfield; BSA; ROF Fazakerley; ROF Theale, Berkshire; Lines Brothers Ltd; Long Branch, Canada plus numerous sub-contractors making individual parts.
Produced	1941 - Version dependent
Number built	3.7-4.6 million (all variants, depending on source)
Variants	Mk. I, II, IIS, III, IV, V, VIS
Specifications
Weight	(Mk. II) 3.18 kg
Length	(Mk. II) 760 mm
Barrel length	196 mm
Cartridge	9 mm Luger Parabellum
Calibre	9 mm
Action	Blowback-operated, Open bolt
Rate of fire	version dependent ~500 round/min
Muzzle velocity	1200 ft/s (365 m/s) non-suppressed versions
Effective range	50 yards (46 m)
Feed system	32 round detachable box magazine

The Sten (or Sten gun) was a family of British, 9 mm submachine guns used extensively by the British Empire and Commonwealth forces throughout World War II and the Korean War. They were notable for their simple design and comparatively low cost of production. The name STEN is an acronym, deriving from the names of the weapon's chief designers, Major Reginald Shepherd and Harold Turpin, and ENfield, the location of the Royal Small Arms Factory (RSAF) at Enfield Lock in London. Over 4 million Stens in various versions were made in the 1940s.

The official designation Carbine, Machine, Sten should not be confused with the common understanding of carbine; the Sten was a typical, almost stereotypical submachine gun while the term carbine is used to refer to short, light rifles.

 History

The Sten was designed at a time when Britain was engaged in the Battle of Britain and other fighting throughout the world, and facing the danger of being invaded by the Nazis. Weapons had been lost during the evacuation from Dunkirk and the army was being expanded. Prior to 1941 (and even later) the British were purchasing all the Thompson submachine guns they could from America, but this 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 a significantly cheaper 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 required a minimum amount of machining and manufacturing effort by using simple pressed metal components and minor welding. Much of the production could be performed by small workshops and the guns 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. Some later versions were not quite as spartan.

The Sten was slowly withdrawn from British service in the 1960s, and was replaced by the Sterling SMG. The other Commonwealth nations made or adopted their own replacements. The Sten was used extensively by Jewish partisans during the Israeli War of Independence. These Stens, and their ammunition, were often produced from scratch in secret factories on Kibbutzim. Many Israeli-made Stens were stamped USA for Unser Sticke Arbeit, Yiddish for "our piece of work", but intended to mislead the British into thinking the United States was supplying the Jewish rebels with munitions.^{[citation needed]}

Design

The Sten gun was chambered for the 9 x 19 mm Parabellum pistol cartridge, which was useful in that captured German ammunition supplies could be used. The Sten was small and could be stripped down into a set of easily concealed components and was therefore particularly suited to partisan operations on the continent. 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 similar Błyskawica SMGs were manufactured in occupied Poland).

The Sten was simple blowback operated, automatic weapon that fired from an open bolt. Single shots and full automatic fire were selected by a cross-bolt type push-button located in front and above trigger. The tubular receiver and the barrel sleeve were made from rolled steel. It was fed from a box magazine attached to the housing on the left side of the gun. Various stocks were used with different models, all steel skeleton and tubular stocks to wooden stocks and pistol grips. The sights were fixed consisting of a rear peep and front blade, zeroed to a nominal 100 yards.^[1]

The Sten was sometimes disparaged by soldiers for having such basic sights, which were not always zeroed for an impact point.^{[citation needed]} However during the kind of point shooting scenarios in which the Sten was often fired, this was less of a problem. Due to the low rate of fire it is easy to fire short controllable bursts with a Sten.

Stoppages could occur due to the magazine which was a direct copy of the one used in the German Erma MP38/MP40. The magazine had two columns of tapered 9 mm cartridges arranged side-by-side in a zig-zag manner. To allow the magazine box to be straight, the front of the magazine was tapered to complement the taper of the cartridges. While other staggered magazines fed from both the left and right positions, the Sten magazine required the cartridges to gradually merge at the top of the magazine to form a single column. 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 could result in deformation of the magazine lips, resulting in misfeeds. Additionally to facilitate easier loading to the great resistance when attempting to push the cartridges down to instert the next one, a magazine filler tool was developed and formed part of the weapon's kit. Modern 9 mm magazines such as those used by the Sterling SMG are curved and feed both sides in order to avoid this problem.

Criticisms of the Sten are mostly based on third-hand anecdotes, embellished and repeated by those with no experience of actually using the weapon^{[citation needed]}. In reality, a well-maintained Sten gun is a devastating close-range weapon. If a Sten does jam with the bolt forward, standard practice to clear it is as follows: tilt the Sten to the right to allow gravity to pull jammed rounds out through the cartridge ejection port, whilst recocking the weapon. Then the weapon is fired again as normal.

The slot on the side of the body where the cocking knob ran was 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 was useful in desert environments where oil attracts dust.

The MK II and MK III Stens could accidentally discharge if dropped whilst the gun was cocked. 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.

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 in order to prevent an accidental discharge issue. However, most changes to the production process were more subtle, designed to give greater ease of manufacture and increased reliability. Sten guns of late 1942 and beyond were highly effective weapons.

Such was the ease of manufacture that the Germans also produced a version of the Sten, the MP 3008, late in the war.

Variants

Sten guns were produced in several basic marks, (though the MKI saw limited service, and the MKIV was never issued) and nearly half of the total produced were of the Mark II. Approximately 4.5 million Stens were produced during the war.

 Mark I

This rare weapon had a conical flash hider and fine finish. It had a wooden foregrip and forward handle (sometimes this was made of steel), as well for a section of the stock. The stock was a small tube outline, rather like the Mark II Canadian. One unique feature was that the front pistol grip could be rotated forward to make the firearm easier to stow. The barrel sleeve extended all the way to the end, where it had conical flash hider. Along the top of the tube surrounding the barrel was a line of small holes and its sights were configured somewhat differently. About 100,000 were made before production switched to the Mark II. Sten Mk I's in German possession were designated MP.748(e).

Mark I:

• Overall Length: 35.3 inches (896 mm)
• Barrel Length: 7.8 inches (198 mm)
• Weight: 7.2 pounds (3.8 kg)

Female worker posing with a Sten Mk II in a Canadian factory, 1942.

Mark I*

This was the first simplification of the Mk I. The foregrip, the wooden furniture and the flash hider were deleted for production expediency.^[2]

Mark II

The Mark II was the most prolific, at 2 million units. It was a much rougher weapon than the Mk I. The flash eliminator and hand guard (grip) of the Mk I were eliminated.

Other changes included a removable barrel which projects 3 inches beyond the barrel sleeve and the magazine housing rotates to form cover for ejection opening.

Winston Churchill test fires a Sten Mk II, 1941. The man in a pin-striped suit on Churchill's left is Walter Thompson, Churchill's bodyguard.

The barrel sleeve was shorter and rather than have small holes on the top, it had three sets of three holes equally spaced on the shroud. Sten Mk II's in German possession were designated MP.749(e).

There were some MkIIs that were fitted with a wooden stock and there was also a silenced version (see below).

Regular Mark II:

• Overall Length: 30 inches (762 mm)
• Barrel Length: 7.8 inches (197 mm)
• Weight: 6.7 pounds (3.0 kg)

 Mark II (Canadian)

During World War II a version of the Sten gun was produced at the Long Branch Arsenal in Long Branch, Ontario now part of Toronto, Ontario. This was very similar to the regular Mark II, but was of slighly improved quality and it had a different stock. It was first used in combat in the Dieppe Raid in 1942.

Mark III

This simple design was the next most commonly produced after the Mark II. It was a simplification of the Mk I. It was made both in Canada and the UK with the latter's Lines Bros Ltd the largest manufacturers. The biggest visual difference from the Mark II, was that the barrel shroud extended farther up the barrel. Its main differences technically were that the barrel was fixed and the body was welded shut along the centre of the top. Captured Sten Mk IIIs in German possession were designated MP.750(e).

 Mark IV

The Mark IV was a smaller version which did not progress beyond the prototype stage. It was near pistol-sized and it had a different configuration with a conical flash hider, a rear pistol grip, a very light stock and a much shorter barrel.

 Mark V

British paratroopers in Oosterbeek during Operation Market Garden armed with Sten Mk Vs

This was commonly issued to paratroopers and was used in Normandy and at Arnhem. Changes included wooden pistol grips including a fore grip, a stock, and a bayonet mount. The forward grip would often snap off. The Sten bandolier that was issued to paratroopers held 7 full magazines.

 Mark VI

• Overall Length: 35.8 inches (908 mm)
• Barrel Length: 7.8 inches (198 mm)
• Weight: 9.8 pounds (4.45 kg)

Foreign built copies and derivatives

Norwegian Sten In German-occupied Norway the resistance, under leadership of Bror With, created a large number of Sten guns from scratch, mainly to arm members of the underground army Milorg. The same was done to some extent in Denmark.

Polish Sten The Polish resistance was provided with numerous Stens of various models by the SOE and the Cichociemni. Between 1942 and 1944, approximately 11,000 Sten Mk IIs were delivered to the Armia Krajowa. Due to the simplicity of design, local production of Polish variants of Sten was started in at least 23 underground workshops in Poland. Some of them produced copies of Mark IIs, while others produced the so-called Polski Sten. The Polski Sten made in Warsaw under command of Ryszard Białostocki were built from a number of legal elements made in official factories or acquired through other means. The main body of the machine pistol was made from hydraulic cylinders produced for hospital equipment. All the pistols were marked in English to disguise their origin and the production facilities. A modernized version of the Sten was produced in Poland under the name Błyskawica.

Gerät Potsdam In late 1944, the Mauser works in Germany started manufacturing a series of copies of British Mk II Sten for diversion and sabotage purposes. The series was nicknamed the Gerät Potsdam and approximately 28,000 weapons were made.

MP 3008 In early 1945, Germany was seeking a cheap machine pistol for the Volkssturm. For that purpose a modified Sten was designed by Mauser and named the MP 3008. The main difference was the magazine attached below the weapon. Altogether, roughly 10,000 pieces were produced before the end of World War II.

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