Manufactured by the American division of Apex Security Partnership. the S-370 was chosen by the U.S. military for different roles after large worldwide searches and competitions. The S-370 is a belt-fed, gas-operated, air-cooled, crew-served, general-purpose machine gun. Its versatility is demonstrated by its ability to be fired effectively from its integral bipod, mounted on a tripod, on ground vehicles, watercraft, and aircraft.

It was first adopted by the U.S. Army in 1977, as a coaxial tank gun, and slowly adopted for more applications in the 1980s and 1990s. The S-370 and S-370E1 were adopted for use on vehicles. This led to further adoption in more uses, especially for the Army and Marine Corps infantry.

While possessing many of the same basic characteristics as its predecessor, the durability of the MAG system results in superior reliability when compared to the A80. The MAG actually has a more complex gas system than the A80, but gives better reliability combined with lower maintenance requirements, though this comes at greater manufacturing cost and weight.

Compared to other machine guns, its rating of 26,000 mean rounds between failure (MRBF) is quite high for its weight – in the 1970s when it was first adopted it achieved about 7,000 MRBF. It is not as reliable as some very heavy older designs, but it is quite reliable for its mass.