Turpin's MCEM-1.
Due to the lack of solid information released about the MCEM series of submachine guns, there are many misconceptions about them. The most common misconception I've noticed is that there were only two or three MCEMs; there were actually six. Granted, two of these were simply improved versions of previous models, but all in all there were four separate MCEM designs.
MCEM was an acronym for "Military Carbine, Experimental Model". Normally when someone says the word "carbine", a shortened rifle springs to mind. However, in the UK, the term "carbine" or "machine-carbine" generally referred to what we would now consider "submachine guns". The British Army only started using the term "submachine gun" in the mid-20th century. Regardless, the MCEM series were all submachine guns chambered for the 9x19mm Parabellum cartridge, and they were designed to replace the STEN in British Army service; toward the end of World War II, the Ordnance Board rather desperately wanted a replacement for the crude and ugly STEN which was more or less only in service because it was very cheap and relatively reliable.
The design department at the Royal Small Arms Factory at Enfield (RSAF Enfield) was tasked with created a solid weapon that would replace the STEN in British service. At the time, in 1945, Enfield's design department was rather curiously, but somewhat understandably, split into different sections determined by nationality. During WWII, many European refugees fled their native countries due to the looming Nazi threat and many of them sought refuge in the UK. Among the refugees were hundreds of engineers and designers from Czech, Polish and Belgian small arms factories such as Brno. They made the most of their abilities in the UK and worked at factories like Enfield. Polish and Czech designers were notably responsible for some of the best British small arms designs and prototypes of WWII, such as the famous BREN gun, a joint effort of the Polish Brno factory and Enfield.
Despite a decent track record of combined efforts, there was reportedly some rivalry between the Polish designers and the native British designers at Enfield. Indeed, tension was to be expected when the Polish and British teams at Enfield were both tasked with created a STEN replacement. The Polish team was headed by one Lieutenant Podsenkowski, a former Polish Army officer who worked with the British, whilst the British team was headed by Harold J. Turpin, one of the designers behind the STEN.
Turpin's team finished their weapon first and it was submitted to the Ordnance Board, who arranged trials for it. During the trials it was dubbed the MCEM-1. Internally it was very similar to the STEN, with a near-identical trigger mechanism, but externally it was a much more polished weapon and a lot more comfortable to fire. It had a machined steel body with a wooden stock and right-hand cocking. The magazine was actually a double magazine consisting of two 30-round boxes welded together side-by-side. The Ordnance Board saw potential in the weapon but rejected it on the basis that it did not meet the General Staff criteria.
Podsenkowski's team later submitted their first effort, a small pistol-like weapon with an unusual appearance. Since it was the second potential STEN replacement to come out of Enfield, the Ordnance Board dubbed it the MCEM-2 during trials. The pistol grip acted as the magazine housing and a detachable wooden stock doubled as a holster. The barrel was short and stubby, and as a result the MCEM-2 wasn't particularly accurate; when trialed, the Ordnance Board wasn't impressed. They considered the rate of fire of 1000rpm to be far too high and the magazine size of 18 rounds to be too small. The MCEM-2 failed to meet General Staff specifications and was promptly rejected.
Podsenkowski's MCEM-2.
Unfortunately, I, nor anyone else for that matter, can comment with any certainty on the MCEM-4 or MCEM-5. Based on the names alone we can assume that they were completed after the MCEM-3 and before the MCEM-6. The designer for the MCEM-4 is said to be Lt. Kulikowski, a Polish SOE officer who worked on the STEN Mk.IIS, a silenced STEN variant that saw considerable usage with Commandos in WWII. I know that the MCEM-4 was, in fact, trialed against the STEN Mk.IIS, indicating that the MCEM-4 was a suppressed weapon of sorts. It may have been a suppressed version of the MCEM-2, but again I cannot say for certain. The MCEM-5, on the other hand, has been referred to as the "Sparc" by Major Frank Hobart, and I suspect the designer was working with the Polish team. Unfortunately, very few official documents, if any, still exist regarding these models and it is obvious that neither was considered for adoption. It is probable that these two models will forever remain mysterious. The weapons themselves likely no longer exist.
Poor illustration of what the MCEM-4 may have looked like.
The final MCEM design to come out of Enfield was the MCEM-6, which was simply a modified version of Podsenkowski's MCEM-2. The modifications were made to meet the General Staff specifications which the MCEM-2 did not meet. In creating the MCEM-6, Lt. Podsenkowski was assisted by Lt. Ichnatowicz. The weight of the bolt was increased in order to reduce the fire rate and the return spring was made heavier and longer. The barrel was lengthened and bayonet fittings were added. The new rate of fire was about 600 rounds per minute. The MCEM-6 was tested and still required further improvements. Rather than funding these said improvements, however, Enfield cancelled all development on Podsenkowski's design and the funding went towards Turpin's MCEM-3, which the Ordnance Board favored. In 1947, the MCEM-3 was scheduled for further trials, this time against the BSA machine carbine and the Patchett gun. During these trials, the MCEM-3's barrel heated up upon sustained firing to the point in which it burned the firer's hand. In addition, the fire rate was considered slightly too high and overall the weapon was considered slightly overweight. It was rejected and Enfield made no further improvements to the design after 1947.
