CODE – 02-131-941

NAME – Sten Mk I

NAME (NATIVE) – T-40 (Developmental name)

COUNTRY OF ORIGIN – Great Britain

DATE OF MANUFACTURE – 1941

CALIBER – 9x19mm

OVERALL LENGTH – 84.5 cm (33.25 in), 79 cm (31.25 in) MkI*

BARREL LENGTH – 19.8 cm (7.8 in)

RIFLING (TYPE & TWIST) – 6 Groove, Right hand twist, 1 turn in 25.4 cm (10 in)

BULLET DIAMETER – 9.02 mm 0.355 in

BULLET WEIGHT – 7.45 g (115 gr)

MUZZLE VELOCITY – 351 m/s (1150 fps) Mk1Z

MUZZLE ENERGY – 458 j (338 ft/lbs)

WEIGHT (EMPTY) – 3.27 kg (7 lbs 3.2 oz) Mk I, 3.18 kg (7 lbs) Mk I*

WEIGHT (LOADED) – 3.93 kg (10 lbs 1.7 oz) Mk I, 3.84 kg (8 lbs 7.5 oz) MkI*

SIGHTS – Front – Inverted “V” blade, Rear – Fixed aperture, set to 91 m (100 yds)

EFFECTIVE RANGE – 183 m (200 yds)

OPERATION – Blowback, fires from open bolt

TYPE OF FIRE – Selective, Semi and Full automatic

RATE OF FIRE – 40 rpm (Semi), 128 rpm (Full)

CYCLIC ROF – 540 rpm

FEED DEVICE – 32 round box magazine, double column, single feed

FEED DEVICE WEIGHT (EMPTY) – 0.30 kg (10.6 oz)

FEED DEVICE WEIGHT (LOADED) – 0.67 kg (1 lb 7.5 oz)

BASIC LOAD – 7 magazines (224 rounds)

LOAD WT – 4.69 kg (10 lbs 4.5 oz)

MANUFACTURER – Singer Manufacturing Co, Clydebank, Glasgow, Scotland.

STATUS – Obsolete

SERVICE – British Military, Home Guard, and Commonwealth

 Major Reginald Shepherd and Harold Turpin were two very influential men in the designing of the most famous British submachinegun of World War II. In the time after Dunkirk, it was vital that Great Britain to manufacture as many small arms as possible in the shortest amount of time. The submachinegun was a type of small arm that could be made very quickly, but the Lanchester was not that kind of weapon. As a copy of a German pre-War design, it required a good deal of machining to produce. Shepherd and Turpin had been involved with the initial design and production of the Lanchester and they immediately saw the problems in the quantity production of the design.

     After having received permission to start the new project, Harry Turpin worked long hours at his home to come up with the design. In seven days, during December 1940, the first basic design was completed.  The core of the new weapon was a simple steel tube. For the prototype, the 3.8 cm (1.5 in) leg of a machinegun tripod was used. On 8 January, 1941, the first prototype Sten, the T-40, was ready to fire, long before the name Sten was even coined. Within a month, testing had been conducted and an order for 100,000 weapons was issued. A second order for another 100,000 Mk I Stens was issued some months later.

     Prior to the beginning of a major product run, pilot production and models had to be completed. The basic design of the weapon was cleaned up for production with tooling and manufacturing techniques put in place for mass production. The production order was issued 6 March 1941 to the Singer Manufacturing Co of Clydebank, Scotland. They would turn out to be the only producers of the design. On 7 March, 1941, the new weapon was adopted as the Carbine, Machine, Sten Mk. I.

     From a statement made by Colonel Shepherd himself in June 1949 comes the origin of the name of the submachinegun. The “S” was from Shepherd’s last name, the “T” was from Harold Turpin’s last name, and the “EN” was for England. That is the final authority for the naming of the STEN gun series.

     The original Mk I model was produced with the Butt, No 1, Mk I that had a two-piece wooden filler handgrip at the wrist. The Butt, No 1, Mk I was only seen on the two prototype weapons and the 24 pre-production models. On the production weapon the Butt, No 2 Mk I that had no such wooden filler, was made from steel tubing, and was lighter, was put in place. The Butt No. 2 Mk 2 “T-stock” seen most often on the Sten Mk II could also be found fitted to the Mk I weapon as all later stocks designed could be fitted to earlier Stens.

     The trigger mechanism was covered with a wooden handguard. In front of the handguard was a pivoting fore grip that could be folded down for use or up along the barrel for stowage. Above the fore grip was the magazine well which extended out to the left side of the weapon. Since the Lanchester used a left-side magazine, the new design did as well. But the magazine used in the new gun was different from that used by the Lanchester. The layout of the new magazine was the same as that of the Lanchester, double column and single feed. In fact, the new design could use the Lanchester magazine if needed. But the new magazine was much shorter than the Lanchester and only held 32 rounds. At that size and length, the new magazine could be carried in the standard infantry pouches of the time where the 50-round Lanchester magazines were too long to fit the pouches.

     A casing surrounded the barrel of the new weapon, perforated with several holes to allow some air to circulate. Very noticeable in the Mark I design is the long conical flash eliminator at the muzzle of the weapon. The flash eliminator has an angular cut across the top of the muzzle to help make the device act as a rudimentary compensator.

      The expectation was that operators would handle the Mk I in the same manner as the bolt-action Lee Enfield rifle. The shooter would support the weapon with his left hand and operate the bolt with this right hand. For this reason, the safety catch at the rear of the cocking handle slot was placed at the bottom of the slot, just above and in front of the trigger. This operated very well for shooters using their right hand to operate the weapon. But with the magazine on the left side, it was necessary to use the left hand to reload the weapon. In a continuous motion, the shooter would reach over with his left hand and cock the weapon, never releasing the firing hand from its grip on the stock. It was not known at the time, but the Mk I Sten would be the only weapon with the safety notch on the bottom of the cocking handle slot.

     Within a few months of the initial manufacture of the Mk I Sten came an order for changes. The wooden handguard was to be replaced with a simple metal stamping that would cover the trigger mechanism. The folding fore grip was to be removed. And the conical flash hider, which was of limited effectiveness and difficult to manufacture, be removed. The new weapon was designated the Sten Mk I* and some 100,000 specimens were produced.