Sten

The STEN (Shepherd, Turpin, ENfield, usually written as Sten) was a British submachine gun designed at RSAF Enfield during World War II. Conceived as a cheap emergency measure to rectify Britain's lack of submachine guns early in the war, the Sten was manufactured in the millions and issued in great numbers to British troops and their allies. It is one of the most widely-produced and widely-copied guns in history.

History

STEN guns were created out of necessity, because the United Kingdom was faced with invasion by the German Army, and they had a very small amount of supplies. The Thompson submachine guns supplied by America were too expensive and not available in sufficient quantities, especially after America entered the war and needed most of them for their own troops. Thus, Enfield was given the task to create a new submachine gun for British forces.

The STEN was designed to be cheap and easy to build, and the manufacturing required for its creation was minimal. Production of the weapon could be mainly preformed at small workshops with whatever metal that the shops happened to have at the time.

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 that 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, as the rearward movement of the bolt caused by the recoil impulse is arrested only by the mainspring and the bolt's inertia. The appearance of the gun is basically just a pipe with a metal loop for a stock, and it did not even have a pistol grip like many submachine guns did (and many still do). Along with that, the horizontal magazine well was a notable part of the gun. Another feature of the gun was the fact that it fired the 9x19mm Parabellum cartridge, the standard German pistol and submachine gun round of the time. This was so that British soldiers could use German ammunition that they came across and captured, making it cheaper to use. This gave assaulting troops and commandos a large supply of ammunition and a lighter footprint because they weren't dropping British or American magazines everywhere. However, this caused problems, as the magazine used the same arrangement style as the MP-40: two columns of 9mm cartridges in a staggered arrangement, merging at the top to form a single column. This made it easy for any dirt that got caught in the taper area to cause feed malfunctions. The gun was disliked by many people, who gave it nicknames such as the "Plumber's Nightmare", the "Plumber's Abortion", or the "STENch Gun". However, the advantage of the STEN was the ability to be easily mass-produced, even when there was a shortage during the war.

The STEN was put into service in 1941 and removed during the 1960s. In 1953, it was officially replaced with the L2A1 Sterling submachine gun, but it wasn't until sometime in the 1960s that it was completely removed from service across the empire.

Addons

The STEN Mk. II was the only common weapon used by British SAS in WWII because of its ability to be equipped with a suppressor.

The STEN was air-dropped by the Royal Air Force to aid rebel groups in Norway, they were called Gutta På Skauen (Boys on the woods) and Milorg (military organisation operating from the occupied Norway during WWII). Their cheap manufacturing cost allowed them to be utilised in this way across occupied Europe, with the French Resistance movement being one high profile receiver of STEN guns.

Variants

Mark I

The STEN Mk.I.

The first STEN, designed by Harold J. Turpin, had wooden furniture and a slanted flash hider. It also had a folding foregrip, a feature that was not seen on most of the subsequent STEN variants. The bolt was cylindrical with a fixed firing pin. These early STENs were generally quite reliable and performed well, but they were quickly replaced by the cheaper STEN Mk.II.

Mark I*

The STEN Mk.IA.

The STEN Mk.I* was essentially the same as the Mk.I, but without the slanted flash hider and wooden furniture. It was made as a means of cutting down production costs. Together with the Mk.I, over 100,000 of these STENs had been manufactured by the end of the war.

Mark II

The STEN Mk.II.

The STEN Mk.II was the cheapest and the most common variant of the STEN gun. It was essentially the same as the Mk.I in terms of design, but it was simplified externally to reduce manufacturing costs, even more so than the Mk.I*. Mk.II STENs had detachable two-groove barrels, rather than the six-groove barrel seen on the Mk.I models, and there was no wooden furniture on the Mk.II. The result was an incredibly simple, light, inexpensive and very effective submachine gun. There were approximately two million Mk.IIs produced overall.

Mark IIS

The STEN Mk.IIS.

The STEN Mk.IIS was a suppressed version of the STEN Mk.II, designed for special operations. It saw service with British and French troops for special operations, and was probably the most widely-used suppressed weapon of the entire war. Another version, made by the SOE, was also designed, but was never serviced except with French special agents. It had a wooden stock.

Mark III

The STEN Mk.III.

The STEN Mk.III was first produced in 1943 by toy manufacturer Lines Bros. Even cheaper and simpler than the Mk.II, the Mk.III had a single-strut stock and a body made of cheap sheet metal that was welded at the top of the weapon. The barrel could not be detached. It was later manufactured by Long Branch Arsenal in Canada.

Mark IV

The STEN Mk.IV.

The STEN Mk.IV was aesthetically a lot different to the previous models in that it had a standard pistol grip and barrel shroud. It was also one of the few STEN variants to incorporate a flash hider. The unusual trigger guard of the Mk.IV was to facilitate for thick winter gloves. It also had a retractable stock. Internally it was identical to the STEN Mk.II. Although the Mk.IV was intended for paratroopers, it never saw service during the war. A suppressed version was also prototyped, but only one of these models was ever made.

Mark IVB

The STEN Mk.IVB was similar to the Mk.IV, but it had a redesigned pistol grip and trigger guard. This was to improve the balance of the weapon. Otherwise, it was exactly the same as the Mk.IV. Both the Mk.IV and the Mk.IVB were rejected for service because they were allegedly uncomfortable to fire.

Mark V

The STEN Mk.V.

The STEN Mk.V was considered the best STEN variant. It was designed in 1944 and incorporated a wooden butt and pistol grip, and redesigned sights taken from a Lee-Enfield No.4 rifle. Internally it was much the same as the previous models. Reportedly very comfortable to fire compared to the Mk.II and Mk.III, the STEN Mk.V saw service with British paratroopers and special forces during the war. Some parachutists were issued models without the wooden butt, but a foregrip instead, to facilitate for firing whilst landing. A bayonet could also be fitted on the Mk.V.

Mark VI

The STEN Mk.VI was essentially the same as the Mk.V, but with a suppressor attached. The suppressor was the same as the one used on the earlier Mk.IIS. The STEN Mk.VI was issued to British Commandos, mostly for quietly eliminating enemy sentries.

Supressed models

Experimental models

Mark II (wooden butt model)

This was a standard STEN Mk.II submachine gun with a wooden butt attached in place of the wireframe steel butt that most Mk.IIs were attached with. This wooden butt model was never serviced, likely due to the cost of producing it.

Mark II (Rosciszewski model)

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)

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

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 was never serviced.

Mark III (wooden model)

This was a STEN Mk.III with an wooden stock, and bayonet fittings. Sling swivels were also added. It was never serviced due to the costs associated with producing it.

Mark III (wooden model II)

This was a STEN Mk.III entirely encased in an unusual bullpup stock, 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 entirely unknown, but it was likely an experiment into increasing the comfort and handling of the weapon.

Foreign copies and derivatives

Argentine

Modelo C.4

STEN MkIIs were licence copied in Argentina by Pistola Hispano Argentino and can be recognised with a wooden handguard in front of the trigger group. It was known as the Modelo C.4. Another variant came with a pistol grip section based on the Ballester-Molina .45 pistol.

Palestine

Copies of the STEN Mk II and STEN Mk V were clandestinely manufactured in Tel Aviv and on various kibbutzim in 1945-48 for use with Haganah and other Jewish paramilitary groups. According to British paratroopers who served in the Palestine Mandate in 1946-47, the STEN copies were found to be of better quality than their own issued weapons.

French

The French "Gnome et Rhône" R5 STEN, manufactured by the motorbike & aeroplane engine manufacturer Gnome et Rhône (SNECMA), came with a forward pistol grip and distinctive wooden stock, although its greatest improvement was a sliding bolt safety, added to secure the bolt in its forward position. Another variant made by MAC (Manufacture d’armes de Châtellerault), were made and tested shortly after WWII. One variant had an unusual stock shape that proved detrimental to the firer’s aim. Internally it was basically a STEN gun but had two triggers for semi/full auto, a grip safety and a foregrip that used MP40 magazines. Another had a folding stock with a folding magazine insert. The trigger mechanism was complicated and unusual. Neither of these prototypes had any kind of success and MAC closed its doors not long after their conception. The French were not short of SMGs after the war; they had some 3,750 Thompsons and STENs, as well as MAS 38s.

Norwegian

In German-occupied Norway the resistance, under the leadership of Bror With, created a large number of STEN guns from scratch, mainly to equip members of the underground army Milorg. In his autobiography, Norwegian resistance fighter Max Manus frequently mentions the STEN as one of the weapons his groups of commandos and resistance fighters used effectively against German troops.

Danish

Several groups in the Danish resistance movement manufactured STEN guns for their own use. BOPA produced around 200 in a bicycle repair shop on Gammel Køge landevej (Old Køge road), south of Copenhagen. Holger Danske produced about 150 in workshops in Copenhagen, while employees of the construction company Monberg & Thorsen built approximately 200 - 300 in what is now the municipality of Gladsaxe (a suburb of Copenhagen) for use by Holger Danske and others. The resistance groups 'Frit Danmark' and 'Ringen' also built significant numbers of STENs.

Polish

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 STEN variants 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 and KIS. The Polski STENs made in Warsaw under the 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. STENs' barrels were also used for SMGs produced in Poland under the name Błyskawica.

Gerät Potsdam

In late 1944, the Mauser works in Germany secretly started manufacturing copies of the Mk II STEN, apparently for deception and sabotage purposes. These weapons were intended to duplicate the British original as closely as possible, including the markings. The series was referred to as the Gerät Potsdam (Potsdam Device) and approximately 28,000 weapons were made – even though the Germans had ample stocks of captured original STENs available. The intended purpose of these copies is now uncertain.

MP3008

In early 1945, Germany was seeking a cheap version of the MP40 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.

AuSTEN Mk1

The Mark I AuSTEN (from "Australian STEN") was a 9mm Australian submachine gun derived from the British STEN gun developed during the Second World War by the Lithgow Small Arms Factory. It externally resembled the STEN but had twin pistol grips and folding stock resembling those of the German MP40. A Mk 2 version was also produced which was of different appearance and which made more use of die-cast components. Although 20,000 were made, the AuSTEN never achieved the success of the competing Australian-designed Owen submachine gun, known as the "Owen Gun".

Imperia

After the Second World War the Belgian Army was mainly equipped with a mixture of British and American submachine guns. The army, wanting to replace them with a modern and preferably native design, tested various designs with the Vigneron M2 and licence-produced FN Uzi being selected. However, the Imperia was an improved STEN with a fire selector and retractable stock.

Sputter gun

A short-lived American invention developed in the 1980s, the Sputter Gun was designed to circumvent the law that defined a machine gun as something that fired multiple rounds with one pull of the trigger. The Sputter Gun had no trigger, but fired continuously after loading and the pulling back of its bolt, firing until it ran out of ammunition. The gun was very short lived as the ATF quickly reclassified it.

Halcon ML-57

The Halcon ML-57 was a simpler derivative of the STEN gun of Argentine origin that was fed from a vertically inserted magazine.

International Ordnance MP2

During the 1970s-1980s, International Ordnance of San Antonio, Texas, USA released the MP2 machine pistol. It was intended as a more compact, simpler derivative of the British STEN gun to be used in urban guerrilla actions, to be manufactured cheaply and/or in less-than-well-equipped workshops and distributed to "friendly" undercover forces. Much like the FP-45 Liberator pistol of World War II, it could be discarded during an escape with no substantial loss for the force's arsenal. The MP2 is a blowback-operated weapon that fires from an open bolt with an extremely high rate of fire.

Cellini Dunn SM-9

The SM-9 is a machine pistol of Guatemalan origin and manufactured by Cellini-Dunn IMG, Military Research Corp and Wildfire Munitions as the SM-90. It is blowback operated, firing from an open bolt and can use magazines from Ingram MAC-10 submachine guns inserted into a similar foregrip that can be rotated 45 and 90 degrees for left/right handed operators. The layout of the receiver is somewhat simpler than that of a STEN with its internal components light in weight enabling a very high rate of fire of 1200rpm. Its forward pistol grip can hold a spare magazine as well as handling the weapon when firing.

Pleter 91

The Pleter submachine gun was created in 1991 when the breakup of Yugoslavia in the midst of emerging war left the newly formed Republic of Croatia with small number of military firearms. Since the embargo prevented the Croatian military from legally buying them on open market (so they were mostly obtained on the world black market, but with significantly higher price and sometimes of questionable quality), to fulfill the immediate need for arms, they tried to resort on quick and simple locally made designs. Despite having a vertical magazine well (designed to accept 32-round double-feed direct copy of UZI magazine, rather than original single-feed STEN-type magazine), analogies with the STEN include a striking resemblance in the barrel assembly and in the bolt and recoil spring. In addition, this gun also fires from an open bolt, and is further simplified by removing fire mode selector or any safety.

SaskSTEN

SMG International in Canada manufactured reproductions of the STEN in six variants. They made copies of the STEN's Mk 1*, Mk II and Mk III, a "New Zealand STEN" (a Mk II/III STEN hybrid, with sights and a fixed magazine housing similar to the Mk III), then branched out into "hypothetical" STEN-guns with a "Rotary Magazine STEN" (a Mk II STEN with a drum magazine attached below the weapon and wooden horizontal forward grip on the left side of the weapon) and the "FRT Gun" (a long barrel STEN with a wooden or Mk 1* type butt stock, a drum magazine attached below the weapon and sliding ramp rear sights). These last two being obviously not STEN reproductions, especially if they included a drum magazine. The "Rotary Magazine STEN" is a vertically fed STEN which uses a modified STEN bolt, which can use either PPSh drum magazines or stick magazines. The FRT gun is essentially a Suomi that uses a STEN trigger mechanism. All SaskSTEN guns fire from an open bolt.

References

Julio S. Guzmán, Las Armas Modernas de Infantería
Weaponology: (Season 2 Episode 7) SAS
Invasion Gun, Collier's Magazine: September 18 1943, P62