Ordnance Notes -- by Bob Stoner GMCM (SW) Ret.

Stoner 63 and 63A 5.56mm Machinegun

The Stoner 63 and 63A 5.56mm machinegun has developed a somewhat mythic status as part of the Vietnam-era SEAL armory. Dr. Eugene Stoner's idea was for a modular, gas-operated, selective firearm that could be made into a rifle, a carbine, a belt-fed machine gun (right or left feed), a squad automatic weapon with top feed (similar to the British BREN gun), a belt-fed medium machine gun, and a solenoid-fired fixed machine gun for vehicle use.

A Stoner 63A assault rifle. Note gas cylinder is on the top as is the cocking handle. (Photo: Mongo’s Stoner 63A Page)
A Stoner 63A Carbine. This uses the same modules as the rifle version with the exception of the shortened barrel. (Photo: Mongo’s Stoner 63A Page)
A Stoner 63A Belt-fed Light Machine Gun. The guns used by the Navy SEAL teams were derivatives of this gun. (Photo: Mongo’s Stoner 63A Page)
A Stoner 63A Commando belt-fed machine gun. This view shows the 150-round snail drum magazine and its feed chute to good advantage. (Photo: Mongo’s Stoner 63A Page)
A Stoner 63A in the medium machinegun role, mounted on the M122 tripod for the M60 GPMG. (Photo: Mongo’s Stoner 63A Page)
A Stoner 63A in the armored vehicle or gun pod role with solenoid trigger. Note the trigger arrangement between the gun trigger and the solenoid. The plug at the end of the wire is the connector for the solenoid’s electrical trigger. Any of the different barrel configurations shown could be interchanged between any of the different setups shown here. (Photo: Mongo’s Stoner 63A Page)

The Stoner 63A Light Machine Gun (top feed) was similar to the British BREN gun in that the sights had to be off set to the left. The ejection port cover is just below the magazine. The Stoner-designed clip-on bipod is shown in this photo. (Photo: Mongo’s Stoner 63A Page)

 The receiver module was the heart of the package. It had a spring-loaded ejection port covers that opened to allow the bolt to eject the fired case to either the left or right depending on the configuration. Lugs attached to the receiver were used to attach the sights, lower receiver group, magazine wells, or top covers and belt feed mechanisms.

Heart of the Stoner: the receiver module. Depending on the configuration, the gas cylinder was positioned either above the barrel (as shown here) or below the barrel. The barrel latch mechanism is the projection just below the last cooling hole in the hand guard. (Photo: Mongo’s Stoner 63A Page)
A SEAL with a Stoner 63A in the Rung Sat Special Zone (RSSZ) below Saigon. This gun has the 150-round snail drum magazine. Left hand feed guns ejected spent brass to the left and links to the right. Sometimes the spent brass would bounce off the feed chute of the snail drum and lodge in the ejection port to jam the gun. The right hand feed cover was developed to fix this problem. After the 150-rounds in the drum were expended, the gunner detached the drum and used the belted ammunition draped across his shoulders. (Photo: US Navy)

Depending on the configuration of the gun, the gas cylinder could be either above or below the barrel. All Stoners used quick-change barrels in various lengths and sizes. All Stoners used the multiple lugged rotating bolt assembly pioneered by the AR-10 and AR-15 rifles.

The Stoner 63 and 63A was manufactured by Cadillac Gage Corporation. (Cadillac Gage also manufactured the V-100 and V-150 four wheeled armored cars used by American Military Police and Vietnamese forces during the Viet Nam War.) The Stoner Weapon System evolved through combat use in Vietnam. The first guns were of the Stoner 63 style and approximately 2,400 were made from 1963 through 1966. An additional 850 Stoner 63A guns were made between 1966 and 1969, and approximately 100 Mk 23 Mod 0 Stoners were made for the Navy’s SEALs in 1969.

A right side photo of a Mk 23 Mod 0 Stoner (right hand feed) with 100-round plastic box magazine. The projection below the forearm is the cocking handle. Guns with the 150-round snail drum magazine fed from the left side; spent brass ejected left and links ejected right. All right hand feed guns ejected links and spent brass to the left. (Photo: Mongo’s Stoner 63A Page)

The Army had two different versions made up for evaluation by its special forces units as the XM207 and XM207E1 in early 1970, but no production figures are available for those pieces. Stoner production ceased altogether by the end of 1971. Total production for U.S. and foreign users would probably in the 3,500 to 4,000 unit range.

Either the Stoner 63A or Mk 23 Mod 0 Stoner with a long barrel. The gunner is from 7th platoon of SEAL Team TWO based at Nha Be. From June to December 1970 7th platoon operated in the RSSZ. The 100-round box magazine attaches sideways beneath the gun. The right hand feed eliminated the fired brass spin back jamming problem of the left hand feed guns. The silver bar beneath the forearm is the cocking handle. (Photo: Mike Taylor)

Most SEAL Stoners were of the belt-fed, light machinegun (LMG) variety such as the Stoner 63A Commando (which had a shortened barrel). The gun used either a 150-round snail drum that attached beneath the gun and fed from the left or a 100-round plastic box that mounted sideways beneath the gun and fed from the right. Experiments were tried with larger or smaller drums and boxes for the "correct mix" of firepower, portability, and reliability.

One of the problems with the snail drum magazine, left hand feed guns was spin back. That is, rounds ejected into the feed chute of the snail drum and sometimes bounced back into the ejection port to jam the gun (links were ejected to the right). On guns with the box magazine, right hand-feed eliminated spin back because both links and brass were ejected to the left without any obstructions.

A clip-on bipod was available for the LMG, but SEAL operators usually did not use it in the field. SEAL operators who used Stoners treated them with the care one lavishes on thoroughbred racing cars such as a Ferrari. Cleaning, lubrication, and inspections of parts were rigorously applied to the Stoners and they responded with awesome firepower.

If there was any criticism of the Stoner, it was that it had a lot of small parts and required a lot of care in order to perform. Later operators of the XM207 series had malfunctions because they did not maintain their Stoners with the zeal the SEALs did with theirs. The pioneering ground broken by the Stoner machine gun lives on today in the forms of the Fabrique Nationale M249 belt and magazine-fed squad automatic weapon (SAW) and its Mk 46 Mod 0 descendant.

STONER 63 and 63A (Mk 23 Mod 0) SPECIFICATIONS:

Weight of gun -- 5.31 kg (11.7 lbs).
Weight of 100-round ammo box (full) -- 1.5 kg (3.3 lbs).
Weight of LMG, sling, and 100-round box -- 6.9 kg (15.2 lbs).
Length (overall) -- 102 cm (40-1/8 in).
Sight radius -- 56.5 cm (22-1/4 in).
Cyclic rate (variable) -- 700 to 1,000 rounds/minute.
Max sustained fire -- 75 to 125 rounds/minute.
Max effective fire -- 150 to 200 rounds/minute.
Max effective range -- 1,100 m (1,200 yd).
Max range -- 2,653 m (2,900 yd).

Members of SEAL Team ONE, X-RAY platoon pose for the camera at Ben Tre in late 1970. There are five Stoner gunners in the photo: two on the left standing and kneeling; two on the right standing and kneeling; one in the middle, back with sun glasses. Both snail drum and box magazines are shown in this photo. These guns appear to be a combination of the Stoner 63A Commando and Mk 23 Mod 0 configurations. (Photo: Gary Hunt)
The M249 Squad Automatic Weapon as built by FN Herstal USA. This gun can use either belted 5.56mm ammunition (developed for the Stoner 63/63A weapons) or the 30-round magazines of the M16-series rifle or M4-series carbine. (The magazine well is located behind the belted ammunition in this photo.)
The Mk 46 Mod 0 light machine gun being built for Special Operations Command (SOCOM) operators. A refinement of the M249 Special Purpose Weapon (SPW) design, the Mk 46 is lighter, does not have the magazine module of the earlier M249, has a shorter barrel assembly, and uses MIL-STD-1993 rails for the mounting of specialized sights, designators, and optics. (Photos: www.world.guns.ru).

© 2005 Bob Stoner R4