SIG MG 710-3

MG 710-3
A SIG MG 710-3 from the Swedish Army Museum.
Type	General-purpose machine gun
Place of origin	Switzerland
Service history
Used by	See Users
Production history
Designer	SIG
Designed	1955–1960s
Manufacturer	SIG
Specifications
Weight	9.25 kg (20.39 lb)
Length	1,143 mm (45.0 in)
Barrel length	559 mm (22.0 in)
Cartridge	7.62×51mm NATO
Action	Roller-delayed blowback
Rate of fire	800–950 rounds/min
Muzzle velocity	790 m/s (2,592 ft/s)
Effective firing range	100 to 1200 m sight adjustments
Feed system	Non-disintegrating DM1 or disintegrating M13 linked belt
Sights	Open type sights with rear sliding tangent

The SIG MG 710-3 is a Swiss 7.62 mm general-purpose machine gun (GPMG) designed and manufactured by SIG - Schweizerische Industrie Gesellschaft (currently Swiss Arms AG). The weapon was developed as a commercial venture primarily for export, since the Swiss Army had already adopted the 7.5 mm MG 51 GPMG (chambered for the 7.5×55mm Swiss Schmidt–Rubin rifle cartridge), produced by the federal arms factory W+F.

Work on the SIG MG 710-3 machine gun (initially designated the Model 55, changed in 1957 to SIG MG 710) began in 1955 and its design was influenced by the MG 45, a late World War II development of the German MG 42 machine gun. These efforts resulted in the SIG MG 710-1 (adapted to use the 6.5×55mm round) and the SIG MG 710-2 (with the 7.92×57mm Mauser cartridge), while the prototype for the final production version which would become the SIG MG 710-3 (chambered in a standard NATO 7.62×51mm caliber) was completed by the mid-1960s. Currently the weapon is in use by the armed forces of Bolivia, Brunei, Chile, Liberia, and Liechtenstein.

The SIG MG 710-3 is an automatic, air-cooled belt-fed weapon operated by roller-delayed blowback and fires from an open bolt. The machine gun's bolt differs from other contemporary designs employing the short recoil method of operation (such as CETME and Heckler & Koch designed weapons), being a 3-piece design that consists of a bolt head with two locking rollers, a striker sleeve and the bolt carrier which is connected telescopically with the bolt head. When a round is chambered pressure from the return spring drives the bolt and carrier assembly forward; simultaneously both rollers engage camming surfaces which drive the rollers outward from their compressed travel position into recesses in the barrel extension. Upon firing, the bolt carrier and striker assembly recoil to the rear and the geometry of the fixed camming surfaces drives the rollers inward unlocking the bolt breech and increasing the speed at which the striker sleeve withdraws relative to the bolt. As the slower bolt continues rearward it impacts the returning striker sleeve (this impact decelerates the bolt).