The Sten Machine Carbine: The Gun that Almost Never Was

This article was originally written for “The Front”, the newsletter of the California Historical Group, and is reprinted here by permission of the editors.

One of the most mass-produced and widely-used firearms of the Second World War was the British Sten Machine Carbine. Ironically, it was almost never created, and only came about in direct response to enemy action.

Towards the end of the First World War, new weapons and tactics were developed in an attempt to break the stalemate of the Western Front’s trench warfare. One of the new concepts was a “trench sweeper”, a light, compact gun capable of automatic fire; pistol-caliber ammunition was used to reduce the weight and bulk of the weapon.  While several nations experimented with such guns, the first to be successful was Germany, with the Maschinenpistole (MP) 18, chambered for the same ammunition as the 9mm Luger.  This weapon was issued to specially-trained Sturmtruppen (“assault troops”) who were intended to infiltrate into enemy trenches and cause as much havoc as possible.

Interest in this new class of weapon continued in the 1920’s and 30’s. In the United States, General John Thompson designed his famous .45 caliber weapon in 1921, with improvements made in 1928.  Unfortunately, the “Tommy Gun” was soon associated with the gangland violence of the American Prohibition era.

Arnhem 1944 2 Para with Mk V

Battle of Arnhem, September 1944.  British Paratroopers with a German prisoner; three of the men carry the Sten Mark V.

Thompson was the first to coin the term “submachine gun” to describe not only his weapon, but the entire class of pistol-caliber automatic firearms; this term is commonly used today. Many countries developed their own submachine guns, such as the Finnish Suomi, although the Europeans tended to continue calling them machine pistols.  The Germans made improvements on the MP 18, which became the MP 28.  The British used the term “machine carbine” for the new weapons – but the military establishment had no interest in them whatsoever.

The British conducted trials on the Thompson, Suomi, and many others. Detailed test results were carefully written and submitted to the War Office for evaluation.  However, these reports were dismissed over concerns for the short effective range – completely ignoring the fact these were specifically intended as short-range weapons.  The War Office wrote that proper soldiers should be equipped with proper rifles, and reiterated the expectation that a British soldier should be able to hit a target at 600 yards, while machine carbines were only effective to around 100 yards.  The War Office concluded that the British Army was not interested in “gangster guns”.

In September 1939, Germany shocked the world, not only with its invasion of Poland, but also with the Blitzkrieg tactics used in doing so.  Many German troops carried the MP 38, the first submachine gun with a folding stock.

The United Kingdom responded by declaring war on Germany and sending the British Expeditionary Force to reinforce their allies in France and Belgium. Shortly after arrival, the BEF submitted an urgent request for machine carbines; the War Office acquiesced and ordered 300,000 Thompsons from the United States.

It was hoped that the US, still neutral at this point, would be able to quickly supply the Thompsons. However, it was a slow and complex gun to produce, and expensive as well.  Additionally, the German Navy refused to recognize American neutrality and targeted supply ships bound for the UK; many of the desired Thompsons ended up at the bottom of the Atlantic.

In May, 1940, Germany invaded France and the Low Countries, once again using their Blitzkrieg tactics.  One of the most spectacular components of the Blitzkrieg was the use of airborne troops, particularly in the assault on the massive fortifications at Eben Emael in Belgium.

The BEF was forced to evacuate back to England from the port of Dunkirk, and a number of French soldiers managed to escape with them. Over time, refugees from across occupied Europe made their way to Britain.  In addition to having to prepare for a possible enemy invasion, the British Government determined to arm and equip the foreign armies in exile.  They also decided to encourage and support any resistance organizations that developed on the enemy-controlled European continent.  Unfortunately, Britain’s heavy industry was already operating at maximum capacity.

The War Office finally realized the need for Britain to produce its own version of the machine carbine. Fortunately, some enemy weapons had been captured, and these were carefully studied by the staff at the Royal Small Arms Factory at Enfield.  The first British-made machine carbine was the Lanchester, which was just a copy of the German MP 28.  About 80,000 of these were built and issued to the Royal Navy for the defense of port facilities.

The Lanchester was an effective weapon, but like the Thompson, based on old technology and slow to manufacture. The designers at RSAF Enfield were determined to create a new weapon, one that was easier to produce.  They studied captured examples of the MP 38 and quickly found that much of the weapon was made from stamped sheet metal, with only certain components made from machined steel.  This was the inspiration they needed, and they designed the Sten Mark I.  “Sten” was a contraction for Shepherd and Turpin, the primary designers, and Enfield, the Royal Small Arms Factory.  The bolt and barrel were machined, but the bulk of the weapon was made from stampings and pressings, spot-welded in place.  It operated on a simple blowback principle, had a fixed firing pin, and like the Lanchester, the magazine was copied from the MP 28.

The first Sten, the Mark I, began production in January 1941 and was approved for issue to British troops in March. However, that same month, RSAF Enfield received a request from the newly-created Airborne Forces to modify the Sten for their use.  Prime Minister Churchill had called for the creation of the British Airborne, inspired by the enemy’s actions at Eben Emael.  The Sten’s design was revised to accommodate the Airborne, but also to make manufacture even simpler; this was the Sten Mark II.  As the Mark II was introduced so soon after the Mark I, few Mark I’s were issued to the troops.

Early Para with Mk II

British paratrooper, 1942.  Notice the Sten Mark II, with the stock removed, carried under the parachute harness.

The Mark II had a detachable barrel and stock, and the magazine housing could rotate 90 degrees which acted as a dust cover for the ejection port. Early paratroopers jumped with a disassembled Mark II strapped to their chest under the parachute harness.  In the early days of parachuting, rifles had to be dropped in containers; being able to jump with a gun on the person was invaluable.  These design aspects also made the Mark II easier to air drop into occupied Europe, and be concealed by the Resistance units.  As it was chambered in 9mm, it fired the same ammunition as the German MP 38 and the later MP 40, and the magazines were interchangeable, making it easy to use captured enemy supplies.

The Mark II was the most numerous of all the Sten variants, with over 2.5 million made. Most of the components were contracted out to hundreds of vendors, with final assembly performed at the Royal Ordinance Factories at Maltby and Fazakerley.  Traditional gunmakers, such as Birmingham Small Arms and Webley & Scott, made the barrels and bolts.  But the other components, made of simple tubes and stampings, were made across the UK in workshops and garages, as opposed to large factories, allowing light industry to provide valuable help to the war effort.

The Mark III, first issued in 1943, was the simplest of all the Stens. It had even fewer parts and took even less production time than the others, but it also suffered from quality issues.  It therefore never replaced the Mark II.  The Mark III had a fixed barrel and an even more rudimentary front sight than the Mark II.

Tommies and Prisoners Normandy

British troops in Normandy, July 1944, with German prisoners.  The two men at the right carry the Mark III version of the Sten carbine.  Photo courtesy the Imperial War Museum.

By 1944, the potential for Germany to invade Britain was well and truly over, and the Allies were preparing their own invasion of the European mainland. Production efficiency could be relaxed in favor of build quality, and the Mark V Sten was created.  This had a wooden stock, as well as a wooden pistol grip and fore grip, very much like the Thompson.  The foresight assembly was taken from the Number 4 rifle; it also used the same bayonet lugs as the Number 4, allowing the spike bayonet to be fitted.  The entire production run of Mark V’s was issued to the Airborne Forces.  Like the earlier Stens, the stock could be removed, making it easier to jump with the weapon.

The Mark IV and Mark VI never left the prototype phase. However, about 4.5 million Stens of all marks were made.  While most were built in the UK, the Mark II was also built in Canada and New Zealand.  The Sten was issued to British troops and men from across the Commonwealth, as well as the many resistance groups.  Despite popular myth, the British never provided the Sten’s design to the Resistance; however, some of the more enterprising of the partisans were able to reverse engineer the simple design and manufacture components, and sometimes even complete guns.

The Sten’s crude appearance led British troops to call it the “Plumber’s Nightmare”, the “Woolworth Gun” and the “Stench Gun”. However, despite its crudeness, it was effective and easy to learn – so long as care was taken.  It was also lighter and more compact than a rifle, making it ideal for specialist troops such as signalers.

Primary consideration in the Sten’s design was for ease of manufacture; use of the weapon was secondary, and there were issues. The selector switch only had two positions, one for single shots and one for automatic fire; there was not a safety setting or any other safety switch.  Instead, there was a notch for the charging handle intended to keep the bolt from going into battery.  Dropping the weapon or otherwise giving it a strong jolt often allowed the bolt to move enough for the charging handle to leave the safety slot, which often resulted in an accidental discharge or “slam fire”.  The magazine lips were prone to damage, which caused feeding problems; this was exacerbated by holding the side-mounted magazine while firing.  It was intended that the gun be held by the barrel shroud, but care had to be taken not to let the small finger slip into the ejection port and get injured by the movement of the bolt*.  Many Mark III’s had a small tab welded next to the ejection port to prevent this issue.

Partisan with Mk II Paris 1944

The liberation of Paris, August 1944.  A French partisan with a Sten Mk II.

If the Sten was handled carefully, it was an effective weapon at short ranges. British units would often exchange a number of rifles for Stens when close combat was likely, such as in towns or the hedgerow country of Normandy.  While the side-mounted magazine was simply copied from the MP 28, it allowed one to use the Sten in deeper cover than similar weapons with a bottom-mounted magazine.

In many respects, the Sten was the perfect gun for its time. The simplest version, the Mark III, could be manufactured in only six “man hours”, and fifteen could be produced for the cost of one Thompson.  Most of the components were made by small shops, allowing heavy industry to concentrate on other weapons and materiel.  The Sten’s light weight and simplicity made it ideal for supplying to the Partisans.  The fact that 4.5 million were made, and that they were used all over the world, is especially remarkable considering the British military establishment never wanted such a weapon in the first place.

*The author has a deactivated Sten Mark II for public displays. Once, at an air show, a Canadian veteran saw the author’s Sten and proudly showed off his still-mangled little finger.

Sten Display

Author’s deactivated Sten Mk II on display at an air show.   The grenades are also inert.

Advertisements