[5] Stoner managed to solicit the help of Howard Carson, in charge of Cadillac Gage's West Coast plant in Costa Mesa, California (where Armalite was also located), in convincing the company's president, Russell Baker, of the feasibility and commercial potential of his new weapons system.

[5] Russell obliged and Cadillac Gage (a subsidiary of the Ex-Cell-O Corporation) established a small arms development branch in Costa Mesa.

[5] Stoner then recruited his two principal aides at Armalite: Robert Fremont and James L. Sullivan (who would later design the Ultimax 100 light machine gun for the Chartered Industries of Singapore).

[6] However, the design team decided to focus on the 5.56×45mm small caliber high-velocity cartridge, as it appeared the new round was gaining mainstream military approval.

[7] The Costa Mesa facility produced 234 Stoner 63s, when production was then moved in September 1964 to the Cadillac Gage plant in Warren, Michigan.

On March 4, 1963, the Department of Defense's Advanced Research Projects Agency made the first purchase of the Stoner 63, ordering 25 units in various configurations.

[5] Trials were performed by the Army Materiel Command (responsible for logistical support for the Marine Corps) at their own test facilities.

[5] The Army submitted recommendations for improvements to the design—these included a stainless steel gas cylinder, a two-position fire selector with separate safety, ejection port dust covers and modifications to the belt feed mechanism.

The solution was to pressure-fill the hollow buttstock with a lightweight urethane foam, imparting structural rigidity and high impact strength.

But soon afterwards, president Nixon announced that the United States would be withdrawing from Vietnam, eliminating the urgency to adopt a new infantry weapon.

[12] Even very early on in its development stage, a small number of weapons were hurriedly pressed into service with the U.S. Navy SEALs deployed to Southeast Asia.

[15] In 1967, Dutch firm NWM (Nederlandsche Wapen-en Munitiefabriek) De Kruithoorn N.V. of 's-Hertogenbosch acquired licensing rights to manufacture and sell the weapon worldwide with the exception of the United States, Canada and Mexico.

The Navy SEALs continued to use the Stoner 63 and had officially adopted the Commando version as the Mark 23 Mod 0 machine gun.

The radial arrangement of locking lugs distributes the firing load evenly around the bolt head and barrel socket, reducing stress and increasing the longevity of these critical components.

There is about 0.2 in (5.1 mm) of uninterrupted free travel calculated to permit the gas build-up in the bore to drop to a safe level before the carrier's cam slot rotates the bolt counter-clockwise to unlock.

Early ammunition boxes were olive drab in color and manufactured at Costa Mesa, this later changed to a black-colored plastic container made in Warren, Michigan.

Several drum-type belt carriers were designed for the left-hand feed system, with a 150-round drum container being the most popular and used frequently by SEALS in Vietnam.

The gas port was drilled larger in an attempt to alleviate this problem; however this had the effect of merely accelerating the piston's initial displacement.

The Rifle, Carbine and AR barrels have no gas valves as they are exclusively used in magazine-fed configurations and do not require the energy surplus levels of belt-fed mechanisms.

With a few exceptions, all the barrels used in the Stoner 63/63A have a six-groove right-hand rifling with a twist rate of 1:12-inch (305 mm), designed to stabilize the lightweight 55-grain M193 projectile, which was standard at the time.

At the Army's request, Cadillac Gage submitted for testing rifles, carbines, and light machine guns, with 1:9-inch (230 mm) twist barrels, respectively designated XM22E2, XM23E2, and XM207E2.

After NWM obtained a license to produce the Stoner 63A, some barrels were manufactured with a 1:8-inch (200 mm) in rifling pitch to be used with heavier experimental bullets.

The front pin holds a flapper-type magazine catch/release (used in the Rifle/Carbine variants and the left-hand feed LMG with a 150-round drum-type belt container), a full dust cover (used with the top-feeding Automatic Rifle or vertically mounted ammo box on any belt-fed system) or a half size dust cover (used with the right-hand-feed bottom box carrier).

The checkered grip is flared at the bottom to prevent the shooter's hand from sliding off and has an internal storage compartment sealed by a hinged cover with a spring-loaded hatch.

The Stoner 63 bipod is a non-locking type that attaches to the gas tube; it does not pivot and has a limited height adjustment feature.

The Rifle and Carbine versions have simple flip-type apertures with settings for 0–300 and 300–500 m contained between large perforated protective ears.

The KCB 70 features a 7-inch (180 mm) long Bowie blade with a clip-point and an integrated wire-cutter, it was inspired by Soviet bayonets for the AKM.

A highly successful multi-purpose tool, it evolved into the KCB 77, a modular design that was adapted to many different assault rifles.

These variants included a carbine, an assault rifle, and various light machine guns feeding linked ammunition from the left or right.

Robinson Armament Co. also produced 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.