Stoner 63 The Stoner 63 is an American modular weapon system created by Eugene Stoner ( one of the designers of the Armalite AR - 15 ) in 1963 , although without any country was mass used , the Stoner 63 was used by the U . S . Navy SEALs and by the USMC in limited numbers during the Vietnam War . Description . Eugene Stoner , one of designers of M16 rifle , left ArmaLite in about 1961 and joined the Cadillac GageCorp . There he began development of an entirely new weapon system . It was probably the first truly modular system , that consisted of about fifteen subassemblies which could be assembled in any configuration , from an assault rifle and short carbine up to a lightweight or even a general purpose machine gun . First prototypes , chambered for 7 . 62x51mm NATO ammunition , appeared in 1962 , known as Stoner 62 . Just a year later Stoner turned out a new system , chamberedfor 5 . 56x45 M193 US service round , and known as Stoner 63 . This system , developed and promoted until the early 1970s , was extensively tested by the US military as the XM22 ( Stoner 63A rifle ) , XM23 ( Stoner 63A carbine ) , and the XM207 ( light machine gun with belt feed ) . The only military application of the Stoner 63 system , however , was the Mk . 23 model 0 belt - fed light machine gun configuration , used in limited numbers by US Navy Special Forces and Marine Corps in Vietnam . In general the Stoner system , while having the advantages of modularity and interchangeability of parts and thus great flexibility in tactical use , is too heavy as a rifle , and too expensive and somewhat over - complicated in general . It is also somewhat dirt - sensitive and requires much attention and maintenance . Overall , some 3 , 500 to 4 , 000 Stoner 63 weapon kits were produced between 1962 and 1971 . The Stoner 63 is more than just a single firearm ; it is a modular kit , which contains about 15 sub - assemblies . Different combinations of those sub - assemblies ( barrels , feed units , trigger units , sight units ) allow the assembly of various firearms on the single receiver unit . The stamped steel receiver contains an universal bolt group , with a multi - lug rotating bolt and a long stroke gas piston with gas tube . The receiver also has several sets of mounting points for attachment of all other sub - assemblies and the quick - detachable barrel . In rifle and carbine configuration , the receiver is so orientated that the gas system lies above the barrel and the feed unit mounting points are below the receiver . In all machine gun configurations , either belt or magazine fed , the receiver is turned “ upside down ” , with the gas system being below the barrel , and the feed unit being above the receiver . In rifle / carbine configuration the Stoner 63 system utilizes a hammer - fired trigger unit , integral with the pistol grip and triggerguard . This trigger unit allows for single shots and full auto fire , and the gun is fired from a closed bolt only . In machine gun configuration , the trigger unit has no hammer ; instead , its sear interoperates with the cut in the gas piston rod , allowing only full automatic fire , and only from an open bolt . The magazine feed unit can accommodate proprietary curved box magazines for 30 rounds , and can be used both in rifle and machine gun configurations . The belt feed unit could be used only in machine gun configurations . Different rear sight units were available for various configurations , with the front sights being mounted on quick detachable barrels . On earlier Stoner 63 system weapons , the charging handle was located on the right side of the bolt carrier ; the safety and fire selector were combined in one control , located on the left side of the trigger unit . On the modified Stoner 63A system , the charging handle was attached to the gas piston rod , and projected from the top in rifle / carbine configuration , or from the bottom in MG / LMG configurations ; the safety was made as separate lever at the front of the trigger guard , with the fire mode selector still located on the side of the trigger unit , above the pistol grip . The Stoner 63 system featured a variety of easily detachable fixed or folding buttstocks . The latter were available in a side - folding plastic variety , or in an under - folding stamped steel type , similar to the Kalashnikov AKS . Variants The Stoner 63 was produced in several configurations , with 15 separate assemblies , which had limited parts commonality . These variants included a carbine , an assault rifle , and various light machine guns feeding linked ammunition from the left or right . The gas system was mounted in different positions depending on the weapon ' s configuration . Due to the multi - role nature of the design the carbine and rifle versions were heavier than comparable weapons of the same type . The most recent descendant of this line is the Stoner LMG produced by Knight ' s Armament Company , which has significant changes from the older Stoner 63 . Robinson Armament Co . also produces the semi - automatic M96 Expeditionary Weapon System which , though technically different , was based on the Stoner 63 design , and thus has some of its features and configurations . Specifications See Also