The EM-2, also known as Rifle, No.9, Mk.1 or Janson rifle, was a British assault rifle. It was briefly adopted by British forces in 1951, but the decision was overturned very shortly thereafter by Winston Churchill's incoming government in an effort to secure NATO standardisation of small arms and ammunition. It was an innovative weapon with the compact bullpup layout, built-in carrying handle and an optical sight.
The gun was designed to fire one of the first purpose-designed entirely new intermediate cartridges, designed to a 1945 requirement as a result of combat experience and German advances in weapons design during World War II. The round, the .280 British, was designed to replace the .303 round, which dated to the late 19th century. The EM-2 was intended to replace the Lee-Enfield bolt-action rifles and various submachineguns, while the TADEN would replace the Bren gun and Vickers machine gun.
As part of NATO standardization efforts, the United States claimed the .280 British round was too weak for use in rifles and machine guns, and instead favoured the much more powerful 7.62×51mm NATO round. A bullpup layout for a British service rifle was finally adopted some years later in form of the SA80 assault rifle, which remains in service today.
Development
Post-war weapons
The British Army entered World War II with infantry weapons based on the .303 British round, including the Lee-Enfield bolt-action rifle, Vickers machine gun and the Bren gun. The .303 had been developed near the end of the 19th century, and had several problems when used in modern designs, notably, the rimmed cartridge design that made it more difficult to use in a magazine. Although the Army had intended to replace the .303 on several occasions dating from before World War I, these efforts were repeatedly put off due to one crisis after another. There had been some consideration of a less powerful cartridge just prior to the start of WWII, using a 7.92 mm bullet, but in the aftermath of the Dunkirk evacuation, any interest in this development ended.
In the immediate post-war period, Royal Small Arms Factory, Enfield began the development of a series of designs firing German rounds. Polish designer Roman Korsak was producing a new light machine gun firing the 7.92×57mm Mauser round using a mechanism similar to the FG 42 known as the EM-1, while Jeziorański was designing an infantry weapon firing the StG 44's 7.92×33mm Kurz, the EM-2. A second infantry weapon was developed by Metcalf, the EM-3, but was not successful.
Intermediate cartridge
As the war ran down, in 1945 the Army formed the Small Arms Calibre Panel (SACP) to develop a new standard calibre for future weapons. Military intelligence suggested that it would be ten years before the Soviets would be ready for another major war, so the time frame for re-equipping was the mid-to-late 1950s. This gave the Panel ample time to test a number of options.
Experience during the war led to demands for a smaller "intermediate" sized cartridge that would allow fully automatic fire from a rifle-sized weapon. The Army demanded a high degree of accuracy due to the emphasis on marksmanship, so the new round was designed to meet the performance of the .303 (7.7 mm) at but at the reduced range of . After testing a variety of designs, they selected a bullet of about calibre and long, with a mass of .
With the release of the SACP reports, interest in the original series of EM weapons ended and a call for weapons based on the new round went out in September 1947. By this time, Korsak had left the original EM-1 program and Kazimierz Januszewski had replaced him and had adopted the anglicized name Stefan Kenneth Janson. Janson's new design was given the name EM-2, in spite of being more closely related to the original EM-1. A new EM-1 was developed by Stanley Thorpe while Eric Hall developed an EM-3. Perhaps due to the confusing re-use of the names, these weapons are often referred to by their designer's names, becoming the "Thorpe EM-1", "Janson EM-2" and "Hall EM-3". As if this were not confusing enough, code names were also assigned, the EM-1 "Cobra", EM-2 "Mamba", while the EM-3 did not proceed and did not receive a name, as was the case for an entry from Dennis Burney as the EM-4.