How a EM-2 Janson Automatic Rifle Works

Wikipedia:

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.

Type Bullpup assault rifle
Place of origin United Kingdom
Service history
In service 1951
Used by United Kingdom
Production history
Designer Stefan Kenneth Janson
Designed 1948–1950
Manufacturer RSAF Enfield
Chambons
Birmingham Small Arms Company[1]
No. built 59[2]
Variants 6.25×43mm, 7×49mm, 7×51mm, 7.62×51mm NATO, .30-06 Springfield, Carbine, HBAR, Winter trigger variant[1]
Specifications
Mass 3.49 kg (7.7 lb)
Length 889 mm (35.0 in)
Barrel length 623 mm (24.5 in)
Cartridge .280 British
Action Gas-operated, flapper-locked
Rate of fire 450–600 round/min (7.5 to 10 /s)
Muzzle velocity 771m/s (2,545 ft/s)
Effective firing range 700 m (770 yd)
Feed system 20-round detachable box magazine
Sights Optical