The Marines and the Stoner in Vietnam

By Kevin Dockery

In the late 1950s, firearms designer Eugene M. Stoner had completed much of his work on the AR-15 rifle. Stoner had a new idea for a family of weapons based on a single common receiver. Having served as an infantryman in the Marine Corps during World War II, Stoner knew about the needs of a fighting man while in combat.

By February 1963, the first firing model of the new weapons system had been produced. Now known as the Stoner 63, the new design was of a family of six different weapons, all based on the same receiver and operating system. Using the basic receiver and a kit of parts assemblies, the Stoner 63 could be set up as a closed-bolt firing carbine with a folding stock and short barrel or a full sized rifle with a fixed stock and long barrel.

Inverting the receiver and changing parts set up a magazine-fed, open-bolt light machine gun, referred to as the Automatic Rifle configuration in later Marine Corps testing. The mag-fed LMG used a top-loaded magazine, much like the British Bren gun, that fed down into the receiver. The sights of the mag-fed LMG were offset to the left so that the operator could aim the weapon past the magazine. The tactical advantages of such a system were that the entire squad could supply ammunition to the gun, already packaged in magazines, from their rifles. Also a very low profile could be maintained by the gunner firing the LMG from the prone position.

Changing the barrel, rear sight assembly, and magazine adapter to a different heavy barrel and adding a belt-feed mechanism top cover, which incorporated a rear sight as part of the assembly, now made the Stoner 63 a belt-fed light machine gun. A plastic box, for which design Stoner received another patent, could be hung from the side of the belt feed tray. This assembly made the Stoner the only light machine gun at the time chambered for the .223 caliber round and it could also be carried and operated comfortably by one man.

At 11.9 pounds empty with wooden furniture and its bipod and sling attached, the Stoner 63 light machine gun weighed only a few pounds more than the then standard US infantry rifle, the M14, while offering a much higher volume of fire. The standard M14, issued with six loaded 20 round magazines (120 rounds total), weighed in at 18.93 pounds. The Stoner 63 LMG weighed only 17.83 pounds with 150 rounds attached in its plastic box. A one-pound weight savings while giving the gunner an additional 30 rounds of ammunition.

There is an almost 2:1 difference in weight between the 5.56mm round and the 7.62mm NATO round. A eight round link belt (M13 links) of 7.62mm NATO has the same weight as a seventeen round link belt of 5.56mm. In addition, the smaller round allows for a much smaller and lighter weapon. This was amply demonstrated by Stoner in the new Stoner 63.

The Stoner 63 was unique in the firearms world at the time of its introduction and caused more than a little interest in some military circles. By March 4, 1963, less than a month after the first firing model of the Stoner 63 was completed, an order was received for 25 of the weapons in various configurations. The order, SS-125, was issued from the Office of the Secretary of Defense’s Advanced Research Projects Agency (OSD/ARPA). The ARPA people already had a great respect for Stoner due to his revolutionary AR-15 design, which they were pushing forward through the military system. The new Stoner 63 looked like an even more promising design with its multiple applications inherent in the system.

By April 1963, Stoner was showing his new weapon to his previous service. At the El Toro Marine Corps Air Base in California, the first Stoner 63 was demonstrated for Brigadier General Walt of the Marine Corps. The Marine Corps were interested in the weapon as a complete system. The Corps felt a family of weapons with a common basis would give them the same training and tactical advantages that Stoner had considered when he had first come up with the concept of the convertible weapon.

Orders for the new Stoner 63 weapons system were very light during 1963. ARPA had ordered 25 various versions of the Stoner 63 for their tests, and that was the biggest order of the year. In early October 1963, the US Air Force ordered two Stoner 63 fixed machine guns with pods holding the weapons and ammunition for trials. Later that same month, two Stoner 63 machine guns were ordered for testing at Aberdeen Proving Grounds. It wasn’t until 1964 that the Stoner 63 was ordered specifically for testing and trials by one of the service branches.

On March 30, 1964, Cadillac Gage received order SS-22 for 60 rifles and 20 complete systems from ARPA, The large order was for weapons to be tested by the US Marine Corps. The Marines had been suitably impressed with the Stoner system and ARPA had agreed with their request to field test the new weapon.

Marine enthusiasm for the Stoner was well received and they took in some of the earliest weapons made. Stoner 63’s, serial numbers 00004 and 00005 are still maintained in the Marine Corps Museum’s small arms collection. Springfield Armory also ordered two fixed Stoner 63s during the Spring of 1964 for test purposes.

In May the Aberdeen Proving Grounds report on the Stoner was made to the Army. In July, the Office of the Chief of Research and Development made his report on the Stoner to ARPA. Neither of these reports listed the weapon in glowing terms. This situation is hardly surprising given that the Army had just recently been forced to accept a number of AR-15 rifles.

The leadership at Cadillac Gage still thought the future of the Stoner 63 looked promising. The manufacture of the weapon centered around sheet metal stamping, forming, and precision welding. The California Cadillac Gage facilities were inadequate to the task of mass producing the new weapon but the company also had a manufacturing facility in Detroit where the mechanical support for such manufacture was easily available. Detroit was the center of the automobile industry and the precision forming and welding of sheet metal was a common practice for such manufacture.

In September, 1964, after some 234 Stoner 63s had been produced and serial numbered, Cadillac Gage moved the production of the weapon to their facilities in Michigan. The Arms Development and Engineering staff, Eugene Stoner among them, moved to the newly set up Weapons Manufacturing Facilities in Roseville, Michigan, just north of Detroit. At this time, the wooden stocks and pistol grips on the Stoner 63 were changed. Grips and stocks were now made of polycarbonate plastic, though the forestock for the machine gun configuration remained black-painted wood.

General Wallace Green, the Commandant of the Marine Corps, had been impressed with the idea of the Stoner family of weapons. This may have come about in no small part due to Cadillac Gage hiring a newly retired Marine Colonel who, during the end part of his military career, spoke to General Green convincingly on the advantages such a system offered to the Corps. Colt at the time, was offering what they called a family of weapons based on the AR-15. But the Colt weapon system, the CAR-15, was made up of specific firearms which could not be interchanged easily. This did not meet some of the advantages of the Stoner 63.

The situation did start to look very good for the future of the Stoner 63 system in 1965. On 23 April 1965, the Army Weapons Command put in an order for 861 Stoner weapons in various configurations for testing as part of the new Small-Arms Weapons Systems (SAWS) program. Within just a few days of this purchase order being issued, the Marine Corps Landing Force Development center (MCLFDC) test report was delivered to Marine Corps Headquarters.

The MCLFDC report recommended the Stoner 63 for further, more advanced, field testing. This report helped fuel the enthusiasm for the Stoner 63 among the Corps Command and Marine Corps Commandant General Wallace Greene in particular. This situation was not well received by the Army Weapons Command who strongly disliked the new AR-15 rifle over the M14 rifle. For the Army, it was now looking like the Marine Corps was going to push for another, completely different, .223 caliber weapon that also could compete with the still new M60 machine gun.

On 20 December, 1965, the Marine Corps put in an order for 1,080 Stoner rifles as well as the parts necessary to assemble other configurations of the weapon. Extensive testing of the Stoner system by the Marine Corps did indicate some weaknesses in the system that needed correction. In the first several months of 1966, these weaknesses were identified and brought to the attention of Cadillac Gage.

While the modification problem was being addressed, the Marine Corps continued their testing of the Stoner 63 system. results from the field were varied, but in general, the weapon system was well liked by many of the men employed in testing it. Substantial tactical and logistical advantages were found in using the system by the evaluation groups. Testers included one rifle company, a platoon of the division reconnaissance battalion, and a platoon of the force reconnaissance company.

An almost immediate change to the fielding of the Stoner weapons system during evaluations was the dropping of the automatic rifle configuration. It was found that the automatic rifle was the least dependable of all of the Stoner 63 configurations. This was due to the top-loading magazine feed used in the automatic rifle. It was found during Marine testing that every time the automatic rifle was loaded, any sand, dirt, or foreign material in the magazine was poured directly into the receiver. With the open bolt of the automatic rifle configuration, this material jammed the action causing an unacceptable number of stoppages.

The remainder of the Stoner 63 weapons system was evaluated by the Marine Corps during March, April, and May, 1967. A comparison testing of the new M16E1 was conducted by the same test groups during June and July of that same year. Test results were tabulated and the report made at the end of August that same year.

Testing showed the Stoner rifle had the advantages of weight, accuracy, improved ammunition, and compatibility with other weapons (the balance of the 63 system), when compared to the standard M14 rifle. The Stoner rifle was found to have a lower reliability than the M14, but this problem was considered correctable with modifications. The difference in reliability between the Stoner 63 and the M14 was not considered significant when considering the overall advantages of the entire system. When compared to the M16E1, the Stoner 63 Rifle was found to be more accurate, more reliable, and had a family of weapons that it was compatible with.

The Stoner light and medium machine gun configurations also received high recommendations by the majority of Marine testers. The Stoner light machine gun was considered a suitable replacement for the automatic rifle configuration in the Marine rifle squad. The LMG and MMG were found to be highly reliable when compared to any other machine gun in the Marine testing environment.

The Marine testing was extensive. Boot Camp trainees were issued with the Stoner and completed their training cycle with it, in the process scoring higher during weapons qualifications than any comparable Marine unit. Stoners were taken into limited combat in Vietnam, where the design was proven to be accurate and reliable in the jungle environment.

The results of the first major Marine Corps evaluation of the Stoner 63 weapons system were very positive. In the words of the evaluation committee;

3. The basic conclusions of the evaluation are that the Stoner family of weapons provides substantial tactical and logistics advantages. There are some relatively minor modifications required prior to acceptance but none of these appears to create any problem. The system received a high degree of acceptance from personnel involved.

4. The Stoner Weapons System is strongly recommended for adoption.

Some of the difficulties with the Stoner 63 had been addressed by Cadillac Gage prior to the evaluations being run by the Marine Corps. The order for evaluation weapons put forward by the Marine Corps in December 1965, had been filled with the available Stoner 63s. The redesign of the Stoner 63 to the Stoner Model 63A was completed in March 1966. Changes from the Stoner 63 to the 63A configuration include;

a. Larger gas port opening b. Chromium plated chamber c. Stronger and better fitting dust covers d. A relieved breech block cam pin e. A gas nitrided bore f. Separate safety in front of trigger guard g. Feed tray machined casting instead of stamped metal h. Three position gas port valve i. Redesigned stock and forearm of polycarbonate material j. Three piece cleaning rod fitted inside of forearm k. ENDURION metal finish on all exposed surfaces l. Bipod locks onto weapon or locks open for stowage m. Right side belt feed mechanism available, exchanges w/left side feed n. Over-the-shoulder assault sling available o. Upper sling swivel attached to front of barrel handle

The removable trigger guard of the Stoner 63, intended for using the weapon when wearing gloves or mittens and easily lost during testing, was replaced with a permanently attached trigger guard. The size of the plastic ammunition box that could be hung onto the side of the light machine gun was reduced from 150 round to 100 rounds. It was found that the larger box was easily struck by the users leg when patrolling and could be knocked off the weapon.

Other changes to the system included replacing the folding stock of the carbine with a wire folding stock that had considerably fewer parts. The cocking handle of the Stoner 63 was the same for all of the weapons in the system. A perforated length of handle with an outward curved end extended along the side of the handguard, right over the gas tube. On the rifle/carbine versions of the Stoner 63, this handle was on the upper left side of the weapon, above the forestock. On the machine gun versions, the cocking handle was at the lower right side of the weapon, just behind the forestock.

For the rifle and carbine versions of the Stoner 63A, the cocking handle had been completely changed from the original. A small lug had been welded onto the operating rod, several inches behind the piston head. The new cocking handle was located on top of the receiver, over the barrel and handguard, where it could be reached by the operator with either hand easily. The new cocking lever rode along a slot cut into the receiver, just below the gas tube, and engaged the lug welded onto the operating rod. A plunger in the center of the operating handle could be pushed down by the operator and used to push the bolt forward to assist it to close.

For the machine gun versions of the Stoner 63A, the cocking lever engaged the new lug on the bottom of the operating rod, but was otherwise in the same place as in the earlier system. The machine gun cocking rod had been made longer so that it could be more easily reached.

The feed cover of the machine gun had been improved in both strength, manufacture, and function. The cap carrier had been redesigned to include a spring plunger mechanism. In the Stoner 63A, the feed cover could be closed with the bolt in any position while in the Stoner 63 the feed cover could only be closed with the bolt in the cocked position to insure no damage to the weapon.

Another change to the feed system of the Stoner 63A was the development of a drum carrier for the ammunition belt. The final drum design would hold a 150 round ammunition belt securely to the bottom of the weapon and feed the belt in smoothly while firing. The drum was made of spun aluminum to keep weight to a minimum and was securely attached to the receiver of the 63A.

To help keep the system from being jammed by excess dirt, spring loaded covers were placed over both the ejection port of the receiver and the link ejection port on the feed cover. The ejection port cover on the receiver would spring open and remain that way as soon as the bolt carrier moved. The cover over the link ejection port only opened when a link was being ejected and otherwise remained closed.

The gas tube of the 63A was made from 17-4 PH stainless steel to minimize corrosion and giving the new tube a silver outside finish. The inside of the gas tube of the 63A was remachined to prevent carbon build up from jamming the gas piston. This allowed the 63A to fire for longer periods of time between cleanings of the gas system. From roughly serial number 2,000, all Stoners produced by Cadillac Gage were built as 63A’s. No changes were incorporated in the markings Cadillac Gage stamped into the receivers of their Stoners and all weapons remained marked “Stoner 63”.

The large number of improvements in the Stoner 63A system made the weapon of even greater interest to the Marine Corps. On 3 October, 1966, Cadillac Gage received an order from the Marine Corps to modify 286 weapons to the new 63A configuration. The new weapons were scheduled for extensive testing under combat conditions in Vietnam. This combat test series was to be completed by May 31, 1967.

On March 3, 1967, a further order was received from the Marine Corps, this one for an additional 8 weapons to be converted to the 63A model. These additional weapons were intended for further testing under controlled conditions to confirm the field trial results. The tests did confirm what had been determined by most of the Marine users. The Stoner 63A was considered suitable for Marine Corps use without further testing.

Cadillac Gage received a further order from the Marine Corps on 19 April, 1967, for ammunition linking systems and spare parts for the overseas support of the 286 63A systems in Marine Corps hands. But shortly after this order was received, the Army Weapons Command declared the Stoner 63 and 63A to not be acceptable for issue at the time.

Without much fanfare, all of the Stoners in Marine hands were to be turned in. The Army was still interested in the Stoner 63A as a light machine gun, but only as a low-priority project. Army tests of the Stoner to approve the system for procurement were considered extremely biased. But for whatever reason, the question of the Stoner in Marine hands was over by the middle of 1967.

This article first appeared in Small Arms Review V5N7 (April 2002)
and was posted online on February 21, 2014


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