The British Janson E.M.2 Automatic Rifle

By Jonathan Ferguson, Armament Research Services (ARES)

Small Arms Technology in the Face of Opposition


Better known than either the Korsak E.M.1 or the Thorpe E.M.1 bullpup firearms covered so far in this series, is the so-called “Janson E.M.2.” It is often incorrectly supposed to be a direct ancestor of Britain’s present-day L85, but in fact, only the concept was retained in the SA80. Stefan Kenneth Janson was the Anglicised adopted name of Captain Kazimierz-Stefan Januszewski, who in 1949 was head of a team of immigrant firearms designers based at Cheshunt, under the aegis of the “C.E.A.D.” or “Chief Engineer & Superintendent of Armaments Design;” in turn part of the Armament Design Establishment (ADE), which had been relocated from RSAF Enfield during the war.

It should be noted that Janson’s E.M.2 was the second weapon to bear the designation. The first, developed c1945-1947, was an inertia-locked blowback design with fluted chamber credited to a Lieutenant Jeziora?ski (whose name was habitually misspelled in official British documents). Work on this original E.M.2 was ordered stopped in 1947, save for a trial to be carried out with a weapon converted to chamber the U.S. T65 cartridge; unfortunately, nothing is known about this weapon. It seems to have been at this point that the weapon was retrospectively dubbed “E.M.2 Jesieranski.” (There is some disagreement on whether “E.M.” stood for “Experimental Model” or “Enfield Model.”) The Jeziora?ski E.M.2 bore two ADE codenames during development: first “Mamba” and latterly (c.1951) “Yellow Acorn.”

Around the same time as this, the Korsak E.M.1 was selected as the starting point for the development of a potential new service rifle. Januszewski, who had worked under Korsak on the E.M.1, was selected to take the helm on this new project. Assisting was Sydney Hance, who would go on to design the original incarnation of the SA80. Leading the Armaments Design Establishment was Colonel Noel Kent-Lemon of the Royal Artillery, who would later shepherd into service the L1A1 Self-Loading Rifle.


Januszewski’s design retained the receiver arrangement of Korsak’s gun, inspired by the FG42 (1st model), with its push-button disassembly latch, rotate-to-remove butt-plate/return...

This article first appeared in Small Arms Review V23N2 (February 2019)
and was posted online on December 14, 2018


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