Sten
The STEN is a British submachine gun chambered in 9×19mm which was used extensively by British and Commonwealth forces throughout World War II and during the Korean War. The Sten paired a simple design with a low production cost, facilitating mass production to meet the demand for submachine guns. As well as equipping regular units, the Sten was distributed to resistance groups within occupied Europe. Its simple design made it an effective insurgency weapon for resistance groups.
The Sten is a select fire, blowback-operated weapon with a side-mounted magazine. Sten is an acronym, derived from the names of the weapon's chief designers: Major Reginald V. Shepherd and Harold J. Turpin, and "En" for the Enfield factory.
Around four million Stens in various versions were made in the 1940s, making it the second most produced submachine gun of the Second World War, after the Soviet PPSh-41. The Sten served as the basis for the Sterling submachine gun, which replaced the Sten in British service from the 1950s.
Name
The Sten gun's name is an acronym derived from Shepherd, Turpin, and ENfield. It was named after the two chief designers, Major Reginald V. Shepherd and Harold Turpin, and the factory where it was developed, the Royal Small Arms Factory in Enfield.History
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 their arsenal at the same time. After the start of the war and to 1941, the British purchased all the Thompson submachine guns they could from the United States, but these did not meet demand, and Thompsons were expensive, the M1928 costing $200 in 1939, whereas a Sten would turn out to cost only $11. 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, and Harold John Turpin, Senior Draughtsman of the Design Department of the Royal Small Arms Factory, Enfield. Shepherd had been recalled to service after having retired and spending some time at the Birmingham Small Arms Company.
The Sten shared design features, such as its side-mounted magazine configuration, with the Lanchester submachine gun being produced at the same time for the Royal Navy and Royal Air Force, 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
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. 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 unintentional discharges inherent in the design. Most changes to the production process were more subtle, designed to give greater ease of manufacture and increased reliability, and the potentially great differences in build quality contributed to the Sten's reputation as being an unreliable weapon. Historian John Warwicker claimed "Exaggerated reports about the unreliability were usually related to the quality of manufacture. Don Handscombe and his comrades in the Thundersley Patrol of the Auxiliary Units rated them more reliable than the Thompson SMG." Sten guns of late 1942 and beyond were 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. Other Commonwealth nations followed suit, either by creating their own replacements or adopting foreign designs.
Design
The Sten is 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 from 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 German MP40, Soviet PPSh-41, and US M3 submachine gun, among others, use the same operating mechanisms and design philosophy of the Sten, namely their low cost and ease of manufacture. Though the MP40 was also built largely for this purpose, Otto Skorzeny went on record saying that he preferred the Sten because it required less raw material to produce and performed better under adverse combat conditions. The effect of putting lightweight automatic weaponry into the hands of soldiers greatly increased 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. The open-bolt firing mechanism, short barrel and use of pistol ammunition severely restricted accuracy and stopping power, with an effective range of only around, compared to for the Lee–Enfield rifle.
Stoppages could occur for poor maintenance, while others were particular to the Sten. Carbon build-up 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, contrary to instruction, 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.
The Sten's magazine, like the Lanchesters, derived from the MP28, originally to use its magazines, which incorporated the faults of the MP28 magazine. The magazine has two columns of 9 mm cartridges in a staggered arrangement, merging at the top to form a column. While other contemporary staggered magazines, such as the Thompson, feed from the left and right side alternately, the Sten magazine requires the cartridges gradually to merge at the top of the magazine to form a column. Dirt or foreign matter in this taper area can cause feed malfunctions. The walls of the magazine lip have to endure the full stresses of the rounds being pushed in by the spring. This, along with rough handling, can result in deformation of the magazine lips, resulting in misfeeding and a failure to fire. If a Sten failed to feed due to jammed cartridges in the magazine, standard practice to clear it was to remove the magazine from the gun, tap the base of the magazine against the knee, re-insert the magazine, then re-cock the weapon and fire 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 runs was also a target of criticism, as the long opening can allow foreign objects to enter. On the other hand, a beneficial side-effect of the Sten's minimalist design is that it will fire without any lubrication.
The selector is a push button type that actuates a sear disconnector to enable firing in semi-automatic. When firing in this mode, the bolt moves rearward tripping on the sear disconnector downwards requiring the user to release the trigger to fire the weapon again. When firing in full automatic, the selector slightly pivots and moves the sear disconnector sideways enabling the trigger to hold the sear in the firing position without interference of the bolt movement. The open bolt design combined with cheap manufacture and rudimentary safety devices also means the weapon is prone to accidental discharges, which proved hazardous. A simple safety can be engaged while the bolt is in the rearwards position. However, if a loaded Sten with the bolt in the cocked position is dropped, or the butt is knocked against the ground, the bolt can move far enough forward to pick up a round and the spring pressure can be enough to chamber and fire the round. The Mk. IV's cocking handle is designed to prevent this by enabling the bolt to be locked in its forward position, immobilising it. Wear and manufacturing tolerances can render these safety devices ineffective. Though the Sten was somewhat prone to malfunction, in the hands of a well-trained soldier, who knew how to avoid the Sten's failings, they were less of a liability as otherwise may be suggested. According to Leroy Thompson, "Troops usually made the conscious choice to keep the Sten with a magazine in place, based on the assumption that they might need it quickly. It might, then, be argued that more troops were saved by having their Sten ready when an enemy was suddenly encountered than were injured by accident. The Sten was more dangerous to its users than most infantry weapons, but all weapons are dangerous".