The Stoner 63 was a remarkably advanced and clever modular firearm designed by Eugene Stoner (along with Bob Fremont and Jim Sullivan) after he left Armalite. The was tested by DARPA and the uS Marine Corps in 1963, and showed significant potential – enough that the US Navy SEALs adopted it and kept it in service into the 1980s. It was a fantastic balance of weight and controllability, offering a belt-fed 5.56mm platform at less than half the weight of the M60. The other fundamental characteristic of the Stoner 63 was modularity. It was built around a single universal receiver component which could be configured into a multitude of different configurations, from carbine to medium machine gun. Today we have one of the rarer configurations, and Automatic Rifle type. In addition, today’s rifle is actually a Stoner 63A, the improved version introduced in 1966 to resolve some of the problems that had been found in the original.
Ultimately, the Stoner system was able to achieve its remarkably light weight be sacrificing durability. The weapon was engineered extremely well and was not a danger to itself (like, for example, the FG-42), but it was prone to damage when mishandled by the average grunt. This would limit its application to elite units like the SEALs, who were willing to devote the necessary care to the maintenance and operation of the guns in exchange for the excellent handling characteristics it offered.