Stoner 63 Ammo
Stoner 63 Ammo
Soon after leaving ArmaLite, Eugene Stoner, one of the United States' most prolific modern military small arms designers, responsible for the design of the AR-15/M16 assault rifles, AR-10 battle rifle and AR-5 survival rifle, among others, devised a concept for a weapons platform that would be built around a common receiver and certain interchangeable components and could be transformed into a rifle, carbine or various machine gun configurations by simply fitting the appropriate parts to the basic assembly.
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. Russell obliged and Cadillac Gage (a subsidiary of the Ex-Cell-O Corporation) established a small arms development branch in Costa Mesa. Stoner then recruited his two principal aides at Armalite: Robert Fremont and James L. Sullivan (who would later go on to design the Ultimax 100 light machine gun for the Chartered Industries of Singapore).
The first working prototype was chambered in 7.62x51mm NATO and completed in 1962. It was designated the Stoner M69W (for no other reason than when turned upside down it reads the same, symbolizing Stoner's vision of a fully invertible receiver). The follow-up design, called the Stoner 62, also chambered in 7.62x51mm, was intended for mass production. However, the design team decided to focus on the 5.56x45mm small caliber high-velocity cartridge, as it appeared the new round was gaining mainstream military approval. Eugene Stoner had previously worked with the cartridge when he designed the AR-15. The weapon system using the smaller cartridge was known as the Stoner 63. The first models were produced in February 1963. The Costa Mesa facility produced 234 Stoner 63s, when production was then moved in September 1964 to the Cadillac Gage plant in Warren, Michigan. With the change in manufacturing plants, polycarbonate plastic was used for the stocks and grips instead of wood. The weapon is covered under U.S. Patent
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. In August and September 1963, the Stoner 63 was sent to the Marines Corps Landing Force Development Center at Quantico for evaluation, where it made a positive impression with its light weight and high ammunition capacity; the Marines favored the rifle and light machine gun configurations. Trials were performed by the Army Material Command (responsible for logistical support for the Marine Corps) at their own test facilities.
Many bugs affected the outcome of the Army trials of the gun: the ammunition requirements proposed were unrealistic and the weapon was expected to perform with an extremely wide range of port pressures, leaving very little power reserve with some ammunition types. For instance, the tracer ammunition used in the Stoner 63 was of such low pressure that it even failed to function reliably in the M16.
These factors severely affected the weapon's reliability. After several months of testing, the Stoner 63 system was ultimately deemed to be unacceptable for service use. 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 upgrades resulted in the improved Stoner 63A, which began production in 1966. Only about 2,000 examples of the initial version were manufactured before the transition to the model 63A
The Stoner 63 series of weapons are gas-operated, air-cooled, belt or magazine-fed and in rifle and carbine configuration, fire from a closed bolt to ensure maximum accuracy, or in machine gun mode, fire from the open bolt position to prevent cook-offs and enhance cooling. The weapon has a rotary bolt locking mechanism with 7 radially symmetrical locking lugs that engage a series of recesses in the barrel extension, and is actuated by a conventional long-stroke piston. 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. Attached to the piston extension is the bolt carrier which is equipped with a curved cam track that guides the bolt's cam pin (retained by the firing pin) and rotates the bolt 22.5° during the movement of the piston to either lock or unlock the bolt from behind the abutments in the barrel socket. Incorporated into the bolt carrier/piston group is an anti-bounce device, consisting of a 4 in (101.6 mm) carbide rod that rides within the piston extension’s hollow interior and moves back and forth during the recoil and counter-recoil cycles, reducing bolt bounce and preventing the possibility of firing out of battery during closed bolt firing (in the Rifle/Carbine models).
When fired, propellant gases from the ignited cartridge following the projectile down the bore are vented through a gas port into a gas cylinder where they drive the piston and bolt carrier rearward. 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. The locking lugs have no pitch therefore no primary extraction occurs during the unlocking sequence. A deeply-seated spring-loaded claw extractor in the bolt head extracts the spent cartridge casing from the chamber and a spring-powered ejector fixed to the front feed mechanism trigger housing ejects the casing. The bolt carrier continues to the rear and compresses the recoil spring on its guide rod.
The Stoner 63 has a unique buffering system contained within the bolt carrier. In front of the carrier cap are a steel shim and a set of 27 saucer-shaped Belleville washers oriented in opposing sets of three, which absorb energy from the piston stroke by deforming into a flat plate when the bolt carrier strikes the receiver’s end cap. When the plates return to their original shape they release a pulse of strain energy which propels the reciprocating parts forward in counter-recoil with a speed only slightly below that of the original recoil velocity. This feature was designed to extend the weapon’s service life, and the plates will function without failure for between 40,000 and 50,000 rounds (depending upon the type of ammunition used and cyclic rates employed).
In the belt-fed configuration, belt movement is produced by a roller riding in the channeled feed arm and is actuated by the reciprocating movement of the bolt. The spring-loaded feed arm is protected by a hinged top cover and is pivoted at its rear end. As the bolt travels back, the front end of the feed arm moves across the feed tray and operates a lever attached to a single set of spring-loaded pawls. These pawls move a cartridge and link over the feed tray’s stop pawl from where they are positioned onto the slotted feed path and held firmly in place by a spring-powered steel plate in the top cover. The cartridge is then pushed out of its link and the empty link is discarded through the link ejection port which is held closed by a spring-loaded dust cover.
The Stoner 63/63A is chambered for the now-standard 5.56x45mm intermediate rifle cartridge. When in the belt-fed role, the weapon would feed from a disintegrating metallic linked belt marked "S-63 BRW" which is a scaled-down version of the U.S. M13 link developed for the M60 GPMG. The Stoner 63/63A will not work reliably with the later M27 link developed for the M249 SAW. The belt is normally contained in a 150-round plastic ribbed container that has a tab allowing it to be clipped on to the side of the left-hand feed tray. 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. Stoner 63A boxes were also black but had a reduced capacity of 100 rounds as the larger container would unbalance the rifle. These can either be attached to the left-hand feed tray or held in a bottom box carrier when using the right-hand feed mechanism. 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. A 250-round drum carrier was also developed by NAWS China Lake, but this proved too heavy and cumbersome. SEALS would also resort to converting RPD belt carriers for use with their Stoners. The detachable magazines used in the Rifle, Carbine and Automatic Rifle models are fabricated from steel and weigh 8 oz (230 g) unloaded. In an effort to reduce weight, aluminum magazines were later developed cutting the weight down to 4 oz (110 g). Standard magazines have a 30-round cartridge capacity but a 20-round magazine was also offered
Barrel interchangeability is one of the main features that provides the Stoner 63 platform its outstanding versatility. There are 5 barrel options available for the system: the Rifle, Carbine, Automatic Rifle (AR) and two types of machine gun barrels, a standard heavy barrel and a short Commando tube. The standard machine gun and AR barrels are 20 in (508.0 mm) in length (not including the flash suppressor). The Commando barrel has a length of 15.7 in (398.8 mm) and is fluted to reduce weight and enhance the barrel's cooling characteristics. This version was sometimes used by the Navy SEALS but was never fully reliable as the gas port is near the muzzle and as soon as the bullet leaves the barrel, gas pressures drop drastically leaving the operating system little to no power reserve. 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 issue was never truly resolved. 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. The standard machine gun barrel has a manually adjustable gas regulator that can be operated by inserting the nose of a cartridge into a hole over the regulator’s lock detent, pushing down on the detent and rotating to the desired position. The gas regulator has three settings: a "slow" cyclic rate of about 700 rounds/min, produced when the narrowest indicator notch is set over the detent; a middle position with an intermediate rate of 830 rounds/min and a third "fouled" position that delivers the largest quantity of propellant gas to the system, resulting in a rate of fire of 865 rounds/min (the use of this setting should be limited as it induces excessive wear on the operating mechanism).
All Stoner 63/63A barrels are gas nitrided and have a quick-detach capability and can be removed in a matter of seconds in field conditions by simply pushing down a latch located on top of the weapon in front of the feed cover and pulling the barrel forward (with the bolt retracted). The chamber portion of the barrel rests on a U-shaped barrel bracket attached to the gas cylinder. The barrel is firmly locked in position by means of a spring-loaded latch (with two nested coil springs) which drives a steel pin into a hole in the barrel socket. All barrels have a gas block to which a bayonet lug and front sight assembly are mounted. The barrels are equipped with a bird cage type flash suppressor with six oval ports. The AR and standard machine gun barrels also have a carrying handle that can be snapped into one of three positions or removed altogether. The black-painted wooden handles are attached to a steel rod via roll pin. 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. The different twist was to test the 68-grain XM287 and XM288 bullets. 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. None of these were ever produced in significant numbers.
The Stoner 63/63A LMG is an automatic weapon that fires from the open bolt and the trigger mechanism permits only fully automatic firing though burst size can be controlled by the shooter. The entire trigger unit has four trigger pins that give the unit its modularity. 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 next two pins retain the timer and hammer, both of which are absent in the open bolt configurations. The final pin acts as the trigger’s axis shaft; the spring-loaded sear pivots on the selector lever’s axis pin. The selector is disconnected when firing from the open bolt and a sliding manual safety installed near the trigger guard disables the trigger when pushed to the rear. The rear portion of the trigger housing serves as a receiver end cap and is used to attach the shoulder stock. The black polycarbonate pistol grip is also attached to the trigger housing. 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.