sentences:  It is believed that prototypes of MCEM-2 were made before the end of WW2, and its derivatives MCEM-4 and MCEM-6 were tested soon after the war.The latter modifications differed mostly in adoption of the rate-reducing mechanism, incorporated into trigger unit; the rate of fire therefore was decreased from 1000 to more realistic 600 rounds per minute.Nevertheless, neither prototype was found suitable for adoption, and several years later British army adopted a more conventional submachine gun, the Sterling-Patchett.