Sergei Gavrilovich Simonov (1894–1986) was a Soviet weapons designer; he is one of the fathers of the modern assault rifle.
Mostly known for the Samozaryadnyi Karabin sistemi Simonova (Russian: Самозарядный карабин системы Симонова), 1945 (Self-loading Carbine, Simonov's system, 1945), or SKS carbine, he also pioneered the assault and semi-automatic rifle field in the 1920s and 1930s, mostly under the supervision of both Vladimir Fedorov and Fedor Tokarev. His early work preceded both the M1 Garand (of 1933), and the later M1 Carbine, AK-47, and M16 series.
Born in 1894 in Fedotow, Simonov began work in a foundry immediately after completing his elementary school studies. By the end of World War I, after completing a basic technician's course of instruction, he began working on a pioneering automatic rifle designed by Vladimir Grigoryevich Fyodorov, the Fedorov Avtomat. After the Russian Revolution, Simonov continued further at the Moscow Polytechnic Institute, graduating in 1924 to work at Russia's giant Tula Arsenal. By 1926 he had become a quality-control inspector at Tula, and by 1927, had been promoted into the Soviet Design and Development Department where he worked directly under Fedorov. The Simonov AVS-36, which entered service in the 1930s would see service in the early part of World War II, up to about 1940 or so where it was replaced by other semi-automatic designs.
During World War II, Simonov designed some firearms of his own; a submachine gun which did not enter production, and a self-loading anti-tank rifle, the 14.5 x 114mm PTRS, which went on to form the basis — in scaled-down form - of the SKS. An earlier semi-automatic rifle was hindered by official insistence on using the powerful 7.62 x 54mm R, which was at that point standard amongst Russian rifles; unfortunately, as had been found with Fedor Tokarev's SVT-40, the round's excessive power was detrimental to reliable, rapid function of a semi-automatic rifle.
By 1943, advances in thinking — which would soon be confirmed by the successful German Sturmgewehr 44 assault rifle - led to the adoption of a shorter, less powerful round, the 7.62 x 39mm M1943 (also known as "7.62 Soviet" or "7.62 short" to differentiate it from several other rounds in 7.62mm calibre). Field trials of the new rifle proved the weapon and, in 1944 a pre-production run of the SKS went to the Byelorussian front for battlefield trials. After some tweaking, it was officially adopted and designated the 7.62 Samozaryadnyi Karabin Sistemy Simonova Obrazets 1945g (translated, "7.62 Self-loading Carbine System Simonov model year 1945"), and chosen as the ideal replacement for the SVT-40.