Month: August 2018

 

Sten, Submachine gun
Sten Mk. II (trigger mechanism cover is missing)
Type	Submachine gun
Place of origin	United Kingdom
Service history
In service	1941–1960s
Used by	See Users
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 Lebanese Civil War Rhodesian Bush War Turkish invasion of Cyprus Indo-Pakistan Wars IRA Border Campaign The Troubles Punjab insurgency
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)
No. 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
Specifications
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; ~500-600 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

The STEN (or Sten gun) was a family of British submachine gunschambered 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, and so also 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 ENfor Enfield.^[1][2] Over four million Stens in various versions were made in the 1940s.

History[edit]

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 meet demand. 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 minimal 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 of 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 has been described as: highly unreliable, prone to jamming, and inaccurate beyond 30 meters. It was unsuitable for guerrilla operations in open country because it encouraged waste of ammunition. But it was easy and cheap to produce – a gun was said to cost fifteen shillings (three quarters of a pound) – and was supplied to the (French) Resistance in huge quantities.^[3]
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.
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.

Design[edit]

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 moves 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 riflecapable 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^[4] or debris in the bolt raceway could cause a failure to fire, while a dirty chamber could cause a failure to feed.^[5] 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 Winston 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.^[6] 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.^[5] 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.^[5] 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.

Variants[edit]

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

Mark I[edit]

The first ever Mk I Sten gun (number ‘T-40/1’ indicating its originator Harold Turpin, the year 1940 and the serial number “1”) was handmade by Turpin at the Philips Radio works at Perivale, Middlesex during December 1940/January 1941. This particular weapon is held by the historical weapons collection of the British Army‘s Infantry and Small Arms School Corps in Warminster, Wiltshire.^[7]
The first model 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 met the 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), the ‘e’ standing for englisch.

Mark I*[edit]

This was the first simplification of the Mk I. The foregrip, the wooden furniture and the flash hider were removed for production expediency.^[8]

Mark II[edit]

The Mark II was the most common variant, with two million units produced. It was a much rougher weapon than the Mk I. The flash eliminator and the folding handle (the grip) of the Mk I were eliminated. A removable barrel was now provided which projected 3 inches (76 mm) beyond the barrel sleeve. Also, a special catch allowed the magazine to be slid partly out of the magazine housing and the housing rotated 90 degrees counter-clockwise (from the operator’s perspective), together covering the ejection opening and allowing the weapon and magazine both to lie flat on its side.

The barrel sleeve was shorter and rather than having small holes on the top, it had three sets of three holes equally spaced on the shroud. To allow a soldier to hold a Sten by the hot barrel sleeve with the supporting hand, an insulating lace-on leather sleeve guard was sometimes issued.^[9] Sten Mk II’s in German possession were designated MP 749(e), the “e” signifying “englisch”. Some Mk IIs were fitted with a wooden stock as this part was desirable and interchangeable with the Mk V. Also, the Spz-kr assault rifle uses the receiver and components from the Sten Mk II.
Regular Mark II:

• Overall length: 762 mm (30.0 in)
• Barrel length: 197 mm (7.8 in)
• Weight: 3.2 kg (7.1 lb)

Mark II (Canadian)[edit]

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, with a different stock (‘skeleton’ type instead of strut type) and improved quality of manufacture. It was first used in combat in the Dieppe Raid in 1942.

Mark II:

• Overall length: 896 mm (35.3 in)
• Barrel length: 198 mm (7.8 in)
• Weight: 3.8 kg (8.4 lb)

Mark III[edit]

This simple design was the next most commonly produced after the Mark II. A result of the manufacturer Lines Bros Ltd stating it could build a modified design that was quicker and cheaper to build than the Mk II, it was a simplification of the Mk I made both in Canada and the UK. Lines Bros Ltd was the largest manufacturer. The biggest difference from the Mark II was the unification of the receiver, ejection port, and barrel shroud that now extended farther up the barrel. 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 V[edit]

Introduced in 1944, the Mk V was essentially a better-quality, more elaborate version of the Mk 2. Changes included a wooden pistol grip, a vertical wooden fore grip, a wooden stock, and a bayonet mount. There was a No4 Lee–Enfield foresight and the weapon was of better quality manufacture and finish than the Mk2 and Mk3. The Sten bandolier issued to paratroopers held seven full magazines.
Another variant of the Mk V had a swivel stock and rear sight mirror intended for firing around corners in urban warfare, similar to the Krummlauf developed by the Germans for the StG 44.

Mark VI[edit]

See Suppressed Models.

• Overall length: 908 mm (35.7 in)
• Barrel length: 198 mm (7.8 in)
• Weight: 4.5 kg (9.9 lb)

Suppressed models[edit]

Mk IIS and Mk VI models incorporated an integral suppressor (“silencer”) and had a lower muzzle velocity than the others due to a ported barrel intended to reduce velocity to below the speed of sound; 305 m/s (1,001 ft/s). The suppressor would heat up rapidly when the weapon was fired and a canvas cover was laced around the suppressor for some protection for the firer’s supporting hand.^[10]

Mk IIS[edit]

The Mk IIS was, as the name suggests, a suppressed version of the Mk II. Captured examples of the Sten Mk IIS in German service were designated MP 751(e).

Mk VI[edit]

The Mk VI (or ‘6’) was a suppressed version of the Mk V. The Mk VI was the heaviest version due to the added weight of the suppressor, as well as using a wooden pistol grip and wooden stock.
The suppressed models were produced at the request of the Special Operations Executive (SOE) for use on clandestine operations in occupied Europe, starting with the Mk IIS in 1943. Owing to their tendency to overheat, they were fired in short bursts or single shots.^[11]
In addition to its use in the European Theatre, the Mk IIS saw service with clandestine units in the Southwest Pacific Area (SWPA) such as the Services Reconnaissance Department and SOE’s Force 136 on operations against Imperial Japanese forces. The Sten Mk IIS was used by the Operation Jaywick party during their raid into Japanese-occupied Singapore Harbour.
The Sten Mk IIS also saw service with the Australian Special Air Service (SAS) in Vietnam.

Experimental models[edit]

Mark II (wooden butt model)[edit]

This was a standard Sten Mk.II submachine gun with a wooden butt attached in place of the wireframe steel butt used with Mk.IIs. This wooden butt model was never put in service, likely due to the cost of producing it.

Mark II (Rosciszewski model)[edit]

This was a Sten Mk.II modified by Antoni Rosciszewski of Small Arms Ltd. The magazine was mechanically operated by the breech block movement. The trigger was split into two sections, with the upper part of the trigger offering full-auto fire and a lower part offering single shots. It was very complex in design and never fielded.

Mark II (pistol grip model)[edit]

This was a Sten Mk.II with a wireframe pistol grip, intended for use with paratroopers. It was compact but predictably uncomfortable to fire.

Model T42[edit]

This was a Sten Mk.II modified with a 5-inch barrel and folding stock, as well as a conventional pistol grip and redesigned trigger guard. It was dubbed the “T42” in prototype phases, but never entered service.

Mark III (wooden model)[edit]

This was a Sten Mk.III with a “Lanchester” type wooden body and butt, and bayonet fittings. Sling swivels were also added. It never entered service due to the costs associated with producing it.^{[citation needed]}

Mark III (wooden model II)[edit]

This was a Sten Mk.III entirely encased in a wooden body, with the only external metal parts being the trigger, barrel, magazine and cocking handle. The trigger and pistol grip were in line with the magazine. The reasons for its creation are likely an experiment into increasing the comfort and handling of the weapon in freezing temperatures.

Mark IV[edit]

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.

Rofsten[edit]

Developed at the Royal Ordnance Factory at Fazakerley (ROF), the Rofsten was an odd Sten prototype with a redesigned magazine feed, ergonomic pistol grip, selector switch and cocking system. The weapon was cocked by pulling the small ring above the stock. A large flash eliminator was fixed onto the barrel, and a No.5 bayonet could be fixed. It was made to a very high quality standard and had an increased rate of fire (around 900 rounds per minute). The Rofsten was made in 1944 as a single prototype and ROF wanted to submit it to trials the next year. Despite better quality there were numerous reliability problems due to the much higher rate of fire. The budget cuts prevented the modifications and this version never got beyond the prototype stage.

Foreign-built variants and post 1945 derivatives[edit]

Argentine Sten[edit]