The SIG 510, Sturmgewehr 57 in Swiss service, was the standard battle rifle of the Swiss Army in caliber 7.5×55mm in the second half of the 20th century which was manufactured by SIGARMS (now SAN Swiss Arms) of Switzerland. It was introduced in 1959 / 1960 and was replaced by the SIG SG 550 in the 1990s. It is based on the same roller-delayed blowback system used in the H&K G3 and CETME rifles. Hastily adopted in response to the Soviet invasion of Hungary in 1956, it was designed to fill the role of a light machine gun, assault rifle, and grenade launcher. Later, the Stgw 57 was also offered for international sales, chambered in 7.62x51mm NATO as the SIG SG 510-4, but this variant has different external parts and was issued to the Armed Forces of Bolivia and Chile, who still use it to this day in a limited capacity.
At the end of the 1950s, the German Bundeswehr purchased 50 examples in 7.62×51 mm NATO and tested them under the designation "G2" in parallel with the Spanish CETME Model A. Like the Swiss models, 40 of the weapons had shoulder rests made of hard rubber, 10 of wood. However, due to the prevailing desire in NATO at the time for particularly light weapons, it was found to be too heavy and rejected.
The battle rifle is considered to be one of the most accurate mass-produced assault rifles available, and is very reliable in harsh climatic conditions at the cost of weight and being extremely over complicated (Sturmgewehr 57 historian Dale Ding notes the rear sight alone has more parts than a whole Makarov PM).
