The Sten Gun

Firepower on the cheap

The British Sten submachine gun (though technically it should be capitalized as STEN) is one of the most distinctive British small arms of World War II. Born out of an urgent need to produce weapons quickly and cheaply after the loss of hardware during the Dunkirk evacuation (Read our earlier article), it became the second most highly produced submachinegun of World War II. (Contrarily to what you might assume, the number one was not the Thompson (Read our earlier article), but the Soviet PPSh-41.)

The Sten was a successful design in that it was extremely cheap and could be manufactured in huge numbers, with somewhere between 3.7 and 4.6 million of them built during the war. It also earned a reputation of unreliability, the extent of which is the matter of some disagreement. Nevertheless, it became an important weapon for British regular troops, commandos and various guerrilla forces fighting in German-occupied Europe.

After the loss of equipment at Dunkirk, and with a potential German invasion on the horizon, Britain needed all sorts of weapons, and she needed a lot. When it came to submachine guns, the American Thompson was available, but production capacity could not match demand, and, at 200 dollars apiece in 1939 and 70 in 1942, it was also pretty pricey.

Enter Harold John Turpin, Senior Draughtsman of the Design Department at the Royal Small Arms Factory, better known as "Enfield" after the town it's located in. On December 2, 1940, Turpin was doodling away on gun designs and had a sudden idea on how to make a trigger mechanism with only two moving parts. He quickly sketched out the mechanism on a napkin, and showed it to his boss the next day. That boss was Major Reginald Shepherd, Inspector of Arms at the Royal Arsenal, Woolwich, and an important figure in the development of many British small arms at the time. Shepherd embraced Turpin's idea for a simpler trigger mechanism, and it became the foundation for the Sten, which the Ministry of Munitions was also very interested in, as it could be built for the equivalent of 11 dollars apiece. 

The weapon was properly named STEN, all in capitals as it was an acronym: "S" for "Shepherd," "T" for "Turpin," and "EN" for "Enfield" – though Shepherd himself later claimed the last part stood for "England." Turpin finished his design by December 8, six days after his initial sketch, and the first firing prototype was ready by January 8 the next year, a truly dazzling development speed.

Now, the Sten was not the only British submachine gun. There was also the Lanchester, a gun based on the German MP 28, which was used by the Royal Navy and the airport security forces of the Royal Air Force. Being designed before the Dunkirk crisis, the Lanchester was more complex, made of higher-quality materials, and more expensive, but its development was further ahead, so both guns went into manufacture. The two actually had interchangeable magazines, though the Lanchester’s held 50 rounds as opposed to the Sten's 32.

Built for cheapness, the Sten had a barebones appearance, made of stamped metal parts and assembled with minor welding. Much of the production could be done in small workshops, with final assembly happening at Enfield. The first company the British government approached was the American Singer Corporation known for its sewing machines. Singer had a factory in Glasgow, Scotland, which Britain wanted to convert to Sten parts production. Singer's management wasn't having any of the idea, since America was still neutral in the war, and, in fact, was selling industrial machinery to Germany. The Cabinet Office reacted by promptly nationalizing the factory, effective next noon, and threatening to jail anyone who wouldn't go along with the changes.

The first Mk I Sten guns were delivered in October 1941, and quickly gathered both appreciation and criticism. The standard issue British rifle was the bolt-operated Lee-Enfield, which had a much lower firing rate than the semi-automatic American M1 Garand (Read our earlier article). Consequently, a British infantry section (the equivalent of a U.S. squad) greatly benefited from the addition of an automatic weapon, at least when it came to close-range fighting. One unlikely fan of the Sten was the German commando Otto Skorzeny, who gained notoriety with actions such as the rescue of Mussolini from Allied captivity (Read our earlier article), and leading an English-speaking group of infiltrators during the Battle of the Bulge. (Read our earlier article) Skorzeny once stated that he preferred the Sten to the German MP 40, as it operated better under adverse conditions.

The Sten also had its weaknesses arising from poor construction early on, or simply the limitation of the cheap design. It sometimes suffered an accidental discharge when dropped or simply just put down; it could sometimes fire in automatic mode while set to single fire, or the other way around. One Sten famously jammed during the assassination of top Nazi official Reinhard Heydrich in Prague in May 1942 by two British-trained and -equipped Czechoslovak commandos. Similar but less famous accidents earned the gun nicknames like "Plumber's Nightmare" and "Stench gun." At the same time, the British clearly thought the gun was good enough, and regular troops, Commandos and British-supplied partisan forces in Europe all made wide use of it.

The Mark I was deemed still too complex despite its simplicity, and an even more stripped-down version was made. The Mark I* (pronounced "Mark-One-Star") removed the handguard, the forward grip, the vent holes, the wooden furniture and the flash suppressor, and came with a simple tube stock.

It should be noted that films often depict the simpler versions, the ones without forward grips, used such that the firer holds the sideways magazine in his left hand to stabilize the gun. This was certainly done sometimes, but was actually incorrect, as it would eventually bend the magazine catch and cause a failure to feed. In the absence of a forward grip, the gun was supposed to be held like a rifle, with the land hand cradling the fore piece. (There seems to be some variation in what grips were accepted based on the individual quirks of different versions, and training manuals also show firing from the hip, though not with the hand on the magazine.)

The Mark II came hot on the heels of the Mark I; in fact, development on it began in March 1941, months before the first Mk Is came off the assembly line. It had two objectives: make the Sten even simpler and cheaper, and to give paratroopers a version that's easier to disassemble and transport. Turpin designed a new barrel that could be removed easily: with the barrel, the stock and the magazine separated from the gun, it all fit into a very small package, and large quantities could be air-dropped to resistance groups in Nazi-occupied Europe. The gun was made even more compact by making the magazine well (the part the magazine is inserted into) rotatable: instead of protruding to the left, it could rotate and point downwards, allowing more guns to be packed in a single crate. Some Mark IIs came with an integrated suppressor at the request of the Special Operations Executive.

The Mk II also came with a bayonet designed just for it – this was most likely intended for commando units, but didn't see much use. Another change was in response to the gun's tendency to heat up very quickly when fired: a leather sleeve was placed over the barrel, allowing the user to hold it without burning his palm. Slightly different versions of the Mk II were also made in Canada (the first of these seeing action in the Dieppe Raid (Read our earlier article)) and China. The Chinese version, known as M38, only had fully automatic fire, and came in two calibers: the original 9×19mm and the Soviet 7.62×25mm.

The Mark III was not very successful. It was slightly lighter than the Mk II and was made of only 48 parts, but paid for it in utility. It was largely designed so that a specific company making stamped sheet metal toys, Lines Bros Ltd., could join production with their own tools. Once again, development was lightning quick with Mk Is still coming off the lines and Mk IIs in early production, and quality control problems became apparent once the Mk III started seeing service. One big problem it had was that the barrel was no longer removable; if it was damaged, the entire gun had to be discarded, with only a few parts scavengeable for future use. Having said that, Lines could produce a Mk III every five and a half hours, and close to 877,000 units were produced before the version was abandoned on the ground that the Mk II was just generally better. The Mk IIs continued to be shipped overseas; the Mk IIIs, which were too bulky for efficient shipping, remained in Britain, and were given to the Home Guard. The Home Guard's previously used submachine guns, the very high quality and sought-after Thompsons bought from the U.S., were, in turn, given to the Commandos.

The Mark IV never got past the prototype stage. It was smaller, comparable more to a pistol than a "regular" submachine gun.

The Mark V, the last version of the Sten, was finalized in 1943, and the first units issued to troops in early 1944. The British military industry was no longer groaning under the strain so badly by this time, and could afford to create a gun that was higher quality and a bit more expensive.

Mk Vs first saw combat on D-Day in the hands of some of the British glidermen who landed behind enemy lines. The Mk V had a real wooden pistol grip and stock, and essentially the nose of a No. 4 Mk I Enfield rifle, with an Enfield front sight and an attachment for the standard Enfield bayonet. "Only" about 527,000 Mk Vs were built, but they were clearly the best and most reliable version of the Sten gun: they went on to serve in the Korean War and remained in the British army until the 1960s. Some Sten Mk Vs came with an integrated suppressor, and others with a rear sight mirror and a swivel stock that allowed it to be fired around corners in urban combat.

The Sten gun had a number of experimental or regional versions, some of which were never fielded. The Austen, short for "Australian Sten," was manufactured in Australia using a die cast process, forcing molten metal into a mold cavity. The Rosciszewski model of the Mk II had a split trigger: pulling the upper half offered automatic fire, while pulling the lower half resulted in single shots.

The Viper Mark I, never used, was extremely simple, encased in a wooden stuck on all sides, and only had fully automatic fire. It was specifically designed for British military police posted to occupied Germany after the war, and was designed to be fire from the hip, with only one hand. The reason why British military police felt they might need to fire an automatic weapon with one hand is not certain, but at least one photo of an MP with a Thompson gun suggest that maybe they wanted to shoot while riding a motorbike.

Several countries produced their own versions of the Sten during or after World War II. Hidden workshops in Nazi-occupied Poland, Denmark and Norway built their own Sten Mk IIs and several guns more loosely based on the design.

Nazi Germany itself built two versions of the Sten. One, codenamed "Potsdam Device," was intended as a cheaper replacement of the MP 40, while the MP 3008 was a last-ditch gun produced in early 1945.

The most surprising gun inspired by the Sten was the "Sputter Gun," an 80s American invention. It used seven parts from the Sten, and was an attempt to circumvent Federal legislation about owning machine guns. The legal definition at the time revolved around the gun's ability to fire multiple shots with a single pull of the trigger. The Sputter Gun tried to dodge this definition by not having a trigger. Pulling a part of the gun (which was not a trigger) caused the weapon to start firing and not stop until the magazine was empty. The ATF quickly cracked down on the idea, but technically, the gun has never been classified as a machine gun, and was never properly outlawed.

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