1940s–early 1950s: Maschinenkarabiner, Sturmgewehr & AK-47

Sturmgewehr 44 (Germany). Its development began in earnest with the Maschinenkarabiner project

Germany, under the Versailles Treaty, was limited to a professional army of long service soldiers numbering only 100,000 men and forbade tanks or military aircraft. This encouraged an approach that emphasised high quality, and reduced emphasis on low cost. Infantry tactics became based on teams of General-purpose machine guns (GPMG) supporting and supported by a section of infantry. GPMG had high rates of fire to permit small numbers of men to fire at long range to defend a wide front. Enemy soldiers, briefly exposed, would be engaged with a high rate burst of fire to cause casualties before they could take cover. Close range assaults would be conducted by units with submachine guns, for greater mobility, and higher rates of fire. This tactical approach was a refinement of the "Hutier" tactics used by Germany in the last year of WWI.

Some of these automatic firearms used pre-existing rounds; others used new intermediate cartridges. Kinetic energy ranged between 1,400–2,100 J (1,033–1,550-foot-pounds), muzzle velocities of 600–800m/s (1,970–2,625 ft/s) and bullets of 7–9g (108–139 grains).

Germany, like other countries, had observed and studied the emerging demand of infantry rifles evolving since World War I, and their factories made a variety of non-standard cartridges, therefore having less incentive to retain their existing calibres. The 7.92x30 mm (Kurz) cartridge was an example of these experiments; in 1941, it was improved to 7.92x33mm Kurz Infanterie Kurz Patrone("Infantry Short Cartridge"). In 1942, it was again improved as Maschinenkarabiner Patrone S, and in 1943, Pistolen Patrone 43mE; then, finally, Infanterie Kurz Patrone 43. The similarity in size between the 7.92x33mm German cartridge and the 7.62x33mm developed for the M1 Carbine is a curious coincidence, but was ultimately nothing more than independent yet similar solutions to the same problem. The 7.92x33mm round used the same cartridge case head as the standard 7.92x57mm Mauser and the bullet was made from the same diameter rod.

In 1942, Walther presented the Maschinenkarabiner ("automatic carbine," abbr. MKb), named MKb42(W). In the same year, Haenel presented the MKb42(H), designed by Hugo Schmeisser as a result of this program. Rheinmetall-Borsig (some said Krieghoff) presented its FG42 (Fallschirmjäger Gewehr 42, sponsored by Hermann Göring) though this was in a different role, and using a heavy7.92x57mm Mauser cartridge, which was not an intermediate round. Wartime tests in Russia indicated the MKb42(H) performed better than the other two. Schmeisser developed it first as the MP43, then MP43/1, and finally as the MP44/Sturmgewehr 44 (abbreviated StG44, or sometimes Stg 44). It immediately entered large scale production. More than 5,000 units had been produced by February 1944, and 55,000 by the following November.

Following the end of the war, Mikhail Kalashnikov developed in 1947 the AK-47, inspired by the concept and layout of the German StG44, but is quite different mechanically. It fired the 7.62x39mmcartridge, which had been developed as model 43 for use in their SKS carbines that were developed by Simonov in 1945 and subsequently adopted as the SKS-45 . The round was similar to the StG44's in that the bullet was an intermediate round of the same calibre as the larger full-size Russian rifle ammunition.

Though it further supports claims that Kalashnikov closely followed his German counterpart, Russian historians point out that Hugo Schmeisser arrived to Izhevsk in late 1947, while Kalashnikov had relocated development of his rifle to the same premises only as late as 1948 (the development itself began in 1943). Still, Schmeisser greatly helped Soviet gunsmiths to master the cold stamping technology, which was extensively used in the AK design (this especially relates to the later stamped receiver variant).^[15]

Mauser had developed several prototype Sturmgewehr 45 assault rifles, first with the Gerät 06 (Device 6) using a roller-delayed blowback mechanism originally adapted from the roller-locked recoil operation of the MG42 machine gun but with a fixed barrel and gas system. It was realised that with careful attention to the mechanical ratios, the gas system could be omitted. The resultant weapon, the Gerät 06(H) was supposedly slated for adoption by the Wehrmacht as the StG45.

The German technicians involved in developing the Sturmgewehr 45 continued their research in France at CEAM. The StG45 mechanism was modified byLudwig Vorgrimler and Theodor Löffler at the Mulhouse facility between 1946 and 1949. Three versions were made, chambered in .30 Carbine, 7.92x33mm Kurz as well as the 7.65x35mm cartridge developed by Cartoucherie de Valence and adopted in 1948. A 7.5x38mm cartridge using a partial aluminium bullet was abandoned in 1947. Engaged in the Indochina war and being the second NATO contributor, France cancelled the adoption of these new weapons. Vorgrimler moved to Spain and began production of CETME Modelo A,B and C precursors of Heckler & Koch's G3 battle rifle and MP5 submachine gun