ABOVE: Unique still from a movie showing the earliest MK42(HS) prototypes tested at the Infantry School at Döberitz, summer of 1942. Note lacking ejection cover and handguard. (Militärarchiv Freiburg)
Of all the “wonder weapons” fielded by the Third Reich in the last desperate days of World War II, only the automatic rifle chambered for the intermediate cartridge was able to achieve a decisive, palpable, instant and permanent success, which results are still seen throughout the world almost 70 years after Berlin fell. The name Sturmgewehr, meaning ‘assault rifle,’ became a universal term for such a weapon in most languages of the world. It all started with the original Sturmgewehr 44, designed by Hugo Schmeisser of the C.G. Haenel in Suhl, Germany.
Many years before WWII started, small arms designers of the world noted that in the real world the power of the rifle round was seldom used to the full extent. The late 19th Century saw the extraordinary surge in rifle shooting distance capability. The introduction of smokeless cartridges with small caliber jacketed bullets extended the individual effective range of fire far beyond the limitations of the open sights. At 2,000 yards, where these bullets were still lethal, a man-sized target would hide completely behind even the thinnest of front-sight blades. At this distance only large, group, soft-skinned targets were ever vulnerable to rifle fire, and these were fired upon in salvoes by whole units of riflemen. After the advent of machine guns, they took over this task as the modern hard-hitting, flat-trajectory cartridges were ideal for machine-gunning enemy at long range. The other group of cartridges for automatic weapons occupied the opposite end of the power spectrum – these were pistol cartridges shot from semiautomatic pistols and soon to be employed in submachine guns. The gap between the two breeds opened up every year, and at the end of the 19th Century there were people determined to bridge that gap by introducing specialized ‘intermediate rounds’ (Mittelpatronen). The first to do research in that area were Friedrich W. Hebler from Switzerland and Austrian Karel Krnka, who were discussing such ammunition as early as 1892. It was still too early then for such consideration because the military only recently converted to rifles firing breech-loaded fixed ammunition and were still obsessed with extending maximum range and velocity of the bullet comparing the fps values of their rifles like tourists nowadays compare the number of megapixels in their digital cameras.
During the WWI, the issue of a totally new class of rifles AND ammunition became a moot point – the front lacked regular ones sorely enough. But then in the Spring of 1918, Hauptmann (Capt.) Piderit, attached to the GPK (Gewehrprüfungskommission, Small Arms Proofing Committee) of the German General Staff in Berlin, submitted a paper in which he argued for the introduction of the immediate round in the German Army, along with a suitable firearm. He pointed out that in the real world of conflict, virtually no firefights took place at over 800 meters distance, and thus half of the performance of the round, capable of launching a bullet over two kilometers from a Gew 98 or a Maxim was simply wasted. A less powerful, smaller, shorter round, would save powder and brass, while soldiers would be able to carry more bullets and gain instant increase in firepower without increasing his already considerable battle load. Less energy means less recoil, enabling semiautomatic or even selective fire rifles (that he, for lack of better name, called it a ‘Maschinenpistole’ even though it is clear from the body of text that he meant it for more powerful ammunition) to substitute Gew 98s, putting up more effective firepower at reasonable battle distances. Nothing transpired from the Piderit report. The Army decided it already had a ‘machine pistol,’ a true one: the MP 18,I chambered for the already available 9mm Luger ammunition and didn’t want another, especially in an exotic chambering.
The subject returned in January 1923, when Infantry Inspectorate set out combat requirements for the Gew 98 successor – smaller and not heavier than a Mauser repeater, mimicking its ballistic performance out to at least 400 meters, and with a magazine yielding 20, or better, 30 rounds. The experiments led by the Swiss in the 1920s and German companies trying to develop an aerial machine gun for intermediate ammunition came handy in the 1930s, when the development of the future infantry rifle started at long last.
RWS proposed two rounds stemming from aerial ammunition developed there, both in 46 mm long case, one with 7mm and the other with 8mm bullet. Additionally, DWM had their own cartridge, the 7mm x 39.1 nicknamed – for whatever reason – the Bergmann round. In 1934, the Gustav Genschow & Co. (Geco) company proposed the fourth round (7.75mm x 39.5) along with a Heinrich Vollmer designed automatic carbine chambered for it, the Model A35 – itself a further development of his earlier SG29 semiautomatic rifle. This was an extremely overcomplicated weapon, which would have surely become a nightmare for the hapless user, should it ever hit the ranks of any army. The military (for once) displayed sound reason and discarded it. But not because it had a blow-forward gas piston and needed a rocker to transit the impulse of the forward-going piston into the bolt-carrier’s rearwards recoil. The reason was that gases were bled through a hole in the barrel wall, something that the German military in the 1930s dreaded more than thousand deaths.
Weird as Vollmer’s A35 was, it worked (in the laboratory at least) and this success did not go unnoticed. The government started its own intermediate round and weapon program. Polte of Magdeburg, Germany’s ammunition giant, was commissioned to develop the round as of spring 1938, and started with a tiny, yet important step, which all the earlier contestants somehow missed – by signing a contract with the Wehrmacht’s Heereswaffenamt (HWA, Land Forces Armament Bureau, the IWG successor). At the same time HWA contracted C.G. Haenel of Suhl to create a suitable weapon, of which 50 pieces were to be delivered by early July 1942 for field testing.
At the same time the HWA presented the requirements for both round and rifle. The weight was to be ‘lower or equal’ to K98k, the length ‘significantly’ shorter, accuracy comparable to K98k out to 400 m, selective fire with a rate of fire (theoretical) under 450 rpm, rifle grenade compatible, reliable in field conditions, easy to maintain, and ‘of straightforward design.’
Parallel development of both weapon and ammunition in two separate companies is always a big challenge for both. It is simply not easy to design a rifle around the yet-to-exist round. However, any slight change that was introduced in any of the two, the other company had no choice but to follow, frequently resulting in delays, as was yet again confirmed by the German intermediate round program.
The Early Trials
In December, 1940, a prototype ‘Maschinenpistolen’ from Haenel and Walther, who joined the race in 1939, was tested at Kummersdorf, the HWA proving ground. The results were disastrous: jams were abundant, several barrels got bulged, and there was one catastrophic failure. The HWA testers blamed it on inferior quality of the ammunition.
In early February 1942, the HWA ordered 10 million rounds for field testing and introduced new nomenclature. The ‘MP42S’ was now known as Maschinenkarabiner 42 (MKb42, Machine Carbine Model of 1942), and the round was 7.9mm Karabinerpatrone 42 (Kar.Patr.42). In early July 1942, at the Infantry School in Döberitz, then at Kummersdorf Proving Ground, field testing and comparative tests of the Polte ammunition and Haenel rifle, dubbed the ‘MKb42(H)’ started. In 3,654 shots fired, there were 11 case separations, 67 duds (of which 56 fired on second trial), and many stovepipes, blamed on the prototype stage of the weapon’s design.
Further development centered on cheaper and simpler production methods. The bullets were of mE (mit Eisenkren, literally iron-cored, meaning mild-steel) to save lead. To save machining time and tools, the cores ceased to be turned, and instead were stamped. The new core, developed by the August Winkhaus Company, was blunt-nosed, which necessitated a new assembly method – and that in turn called for virtually a new bullet, but the savings were more than worth the effort.
The resulting cartridge was again introduced into the inventory of the Wehrmacht as a Maschinen-Karabiner Patrone “S” (M.Kb.Patr. “S”), only to be re-named again in 1943 to Pistolenpatrone 43 mE when the whole program was re-classed as a Maschinenpistole 43 (MP43) or Submachine Gun, Model of 1943. It wasn’t the last name, however, as in early 1945 the SMG name was once again dropped in favor of the famous Sturmgewehr moniker, and the round was then named the Kurzpatrone 43 (Short Round, Model of 1943).
The MKb42 According to Haenel
Parallel to the cartridge development at Polte, a team of designers at C.G. Haenel Waffen- und Fahradfabrik in Suhl, directed by the company’s manager and chief designer, Hugo Schmeisser, developed a weapon to shoot it. It was a selective fire gas-operated automatic, with gas tube running above the barrel, firing from open bolt position, with a vertically tilted bolt to lock breech block. Open bolt means that between the shots the bolt is held to the rear by the sear – a design concept usually used in weapons meant to fire mostly long bursts, like true machine guns, to enhance cooling between the shots. The downside of the open bolt system is decreased accuracy in semiautomatic fire, due to having a large mass (bolt or bolt and bolt carrier) cycling before each shot, jarring the weapon at the instant of firing. This was possibly a legacy of Hugo Schmeisser’s vision of the Maschinenpistole, as embodied in his previous open-bolt landmark designs, such as the MP 18,I and MP 38 (which was not his design, but nevertheless used some of his ideas). There are more MP 38-style details as well, including the external muzzle thread for blank firing device, form of the magazine well, L-shaped safety cut-out to insert the handle of the cocked bolt and telescoping operating spring cover (evident in early drawings). The gas mechanism is comprised of a gas block pinned on top of the barrel, with gas tube guiding a long-stroke gas piston to the rear opening of the gas chamber, in which gases passing from the barrel by hitherto anathemas gas opening pressed against the piston head. The piston itself was placed at the end of the very long operating rod, connected with a bolt carrier. The bolt carrier governed the bolt locking and unlocking, while the bolt carrier’s projection served as a hammer to blow upon the bolt’s free-floating firing pin. The gas block access was granted by a curious tubular plug, screwed in from the front of the gas block, and reaching all the way forward to the front sight base, forming sort of over-under shotgun layout with the barrel underneath.