The STEN (Shepherd, Turpin, ENfield/ENgland, usually written as Sten) was a British submachine gun (or, under British nomenclature, "machine carbine") 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.
In late 1939, shortly after the beginning of World War II, the British Expeditionary Force in France became concerned by reports that the Germans were arming their troops with large numbers of inexpensive MP38 submachine guns. Worried that they would have no equivalent weapon to match the German SMG, the BEF hastily arranged field trials for several submachine guns, quickly settling on the Thompson submachine gun. The British Ordnance Board proceeded to order quantities of Thompson guns from the United States.
However, after the BEF's retreat from France in 1940, the Army realized that a cost-efficient, domestically-produced SMG was required to match the MP38's production rate. Initially, the Lanchester, a copy of the German MP28 was developed and was adopted by the Navy and Air Force, but was declined by the Army, who desired a cheaper gun. The Army became invested in a design being developed at RSAF Enfield, commissioned by the head of the Small Arms Group, Major Reginald Vernon Shepherd, and designed by draftsman Harold John Turpin. This gun was subsequently named the "Sten", after Shepherd, Turpin, and Enfield.
In January 1941, the first prototype Stens were ready and were tested at Enfield on the 10th and Hythe on the 21st. The Army was quick to approve of the weapon and it was taken into service. This first iteration was known as the Mk.I and incorporated wooden furniture, a hinged foregrip, and a flash hider; these features were deemed to be inessential and in August 1941 a cheaper model, the Mk.II, was demonstrated at Pendine. The new Mk.II was proposed to cut back the production cost significantly by removing the inessential features of the Mk.I. Although the Mk.II Sten was even cruder and less reliable than its already very basic predecessor, it was nonetheless taken into service on account of its inexpensive cost and fast production rate.
The Mk.II Sten became the standard service SMG of the British Commonwealth forces during the war. It saw its first combat use by Canadian troops during the Dieppe Raid on the 19th of August 1942. Although the initial response in Britain to the Sten was optimistic, with some officers even anticipating that it could help turn the tide of the war, the feedback from the troops who were issued the gun was less enthusiastic. It earned a variety of derogatory nicknames, including the "Plumber's Nightmare", due to its unsophisticated appearance and relatively poor reliability.
However, the extremely cheap cost and basic design of the Mk.II Sten ensured that it saw incredibly widespread use, with over 2,000,000 models being produced in total. The Allies supplied anti-Nazi resistance networks in Europe with large quantities of Sten guns, and the simplicity of the design was ideal for untrained partisans. Workshop-built copies were also produced in large quantities in occupied territories like France, Denmark, Italy, the Netherlands, and Poland. A suppressed version of the Mk.II Sten was commissioned for use by Commandos; this was developed at Enfield by a Polish engineer, Lt. Kulikowski. The silenced Sten was taken into service as the Mk.IIS and was the most widely-used suppressed weapon of the war.
In 1943, a toy manufacturer, Line Bros., was commissioned to produce an even simpler model of the Sten that was constructed from minimal components. The body of this gun was made from a single riveted tube of sheet metal, welded at the top. This was taken into service as the Mk.III Sten and was, along with the Mk.II version, produced in extremely large volumes, both in the UK and Canada. It was originally supposed to supersede the Mk.II, but production of the Mk.II continued to take priority, as production issues with the Mk.III were reported. The same year, two experimental models derived from the Mk.II, known as the Mk.IVA and Mk.IVB, were developed for the 1st Airborne Division; these were tried at Pendine but were never adopted.
The final two models of the Sten, the Mk.V and Mk.VI, were developed in late 1943 and entered service in 1944. Rather than simplifying the design, as previous models had done, the Mk.V was a more polished and expensive variant that incorporated wooden furniture, including a foregrip, and a slightly redesigned trigger group. It was built to a considerably higher standard than the Mk.II and was reportedly of much better reliability. The Mk.V was primarily issued to paratroopers, and saw extensive use during British operations in Normandy and Arnhem. The Mk.VI variant was simply a suppressed version of the Mk.V, built following the same principles as the Mk.IIS.
A highly-modified variant of the Sten, known as the ROFSTEN, was proposed by ROF Fazackerley in late 1944 as a potential post-war service model, but this version was never developed any further. In 1945, Nazi Germany began producing its own domestic copy of the Sten, the MP 3008, as a replacement for the MP40. In the post-war period, the Sten continued to see widespread circulation and copy, especially by guerrilla forces.
As early as 1942, the Ordnance Board were considering replacements for the Sten; it was never intended to have a long service life and was seen as a wartime stop-gap. When the war finally did end in 1945, arrangements were swiftly made to trial several new submachine guns. The Army finally settled on the Sterling submachine gun in 1951, and the Sten was taken out of general service in 1953.
Although the Sten was quickly replaced in British service by the Sterling submachine gun after World War II, the widespread distribution of the gun across the world ensured that it served as the technical basis for countless post-war submachine gun designs. The simple production methods and cheap cost of the Sten made it very attractive on the post-war market, especially given the considerable economic toll suffered by many countries involved in the war. Therefore, many companies produced similar weapons or outright clones in an attempt to capitalize on the success of the gun. Home-made submachine guns patterned after the Sten also remained popular among insurgency groups.
For a list of Sten derivatives and copies, see Category:Sten Derivatives.
The Sten was an incredibly basic, blowback-operated submachine gun that fired from an open bolt with a fixed firing pin. This means that the bolt remained to the rear when the weapon was cocked, and on pulling the trigger the bolt flew forward under spring pressure, stripping the round from the magazine, chambering it and firing the weapon all in the same movement. There was no breech locking mechanism, as the rearward movement of the bolt caused by the recoil impulse was arrested only by the mainspring and the bolt's inertia.
A common issue plaguing the Sten was the poor quality of the magazines; these double-stacked and made from stamped steel. The build quality of the magazines was very brittle and the feed lips were prone to malformation, causing frequent stoppages. They were also susceptible to sand and mud, causing increased friction on the magazine spring movement and the bullet feed. These problems were exacerbated by a common tendency among troops to use the magazine as a forward grip. The Sten could also accept MP40 magazines without modification, which allowed users of the Sten to requisition ammo and magazines from captured German stockpiles or fallen foes.
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.
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.
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.
The Sten Mk.IIS (S standing for "special purpose") was an integrally suppressed version of the Sten Mk.II, designed for special operations. It was issued to Commandos and SOE agents operating in occupied territories, such as France. It was predominantly used for eliminating lone sentries during raids on German encampments or checkpoints, and had an effective range of no more than 100 meters. It was the most widely-used suppressed weapon of the entire war.
The suppressor was designed at RSAF Enfield by Lt. Wikter A. Kulikowski and Col. John Henry Icke. It had a drilled barrel which was jacketed by a series of metal baffles that extended past the muzzle of the barrel. The baffles were encased by two outer jackets, and a rubber sealing plug was placed at the end of the jacket. Upon firing, the gases from the bullet would escape through the vents in the barrel and were absorbed by the baffles and prevented from escaping by the rubber plug. The build-up of gas within the suppressor meant that it was prone to overheating in automatic fire, so an asbestos-lined canvas sleeve was often issued to fit over the suppressor and protect the user's hand. Users were trained to fire only single shots unless an emergency called for full-auto fire.
The decreased pressure applied to the bolt meant that the regular Mk.II Sten bolt was too heavy for the Mk.IIS and would not function adequately. To remedy this, a Mk.IIS had a lighter bolt than the standard Mk.II and had two less coils in the return spring.
The SOE independently developed their own suppressor for the Sten that was different in design and saw issue with special agents operating in France. It was detachable and could be fitted to the Mk.II, Mk.V, and Austen. Copies of the Mk.IIS feeding from MAT-49 magazines were used by US special forces in the Vietnam War.
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.
The Sten Mk.IVA 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.
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.
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.
A version of the Mk.V with a hinged stock was also developed, designed for shooting around corners.
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 late in the war. Similarly to the Mk.IIS, a version with a detachable suppressor was also devised by the SOE, but only saw limited use.
The T42 was a modified prototype version of the Sten Mk.II that was designed in an attempt to fix the magazine problems of the Sten. The magazine feed was redesigned to accept experimental single-stack magazines of 15 rounds. The trigger group was also redesigned with a pistol grip and a folding stock was fitted. It was not accepted into service, as the decreased magazine capacity was not seen as a suitable trade-off for the marginally increased reliability.
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