The AR-15/M16/M4 series rifle is undoubtedly the most popular rifle in the United State for all military, law enforcement and commercial markets.  It is the most versatile platform of a rifle on the face of the planet.  Another rifle has crept up into that popularity; one that was on the scrap heap of the U.S. Army for nearly 40 years.  That would be the one that started it all, the AR-10.  “Tomorrow’s Rifle Today” in the late 1950s has turned out to be today’s rifle today.  The rifle that Ordnance Corp would dismiss in the late 1950s would have its day in the late 1990s and in the new millennium would serve as the primary sniper rifle for the U.S. Special Operations Command as well as the U.S. Army, replacing M24 bolt action rifles.  But where did all this begin?

In 1953, George Sullivan gained interest from Richard Boutelle of Fairchild Engine and Aircraft for his idea of developing a small arms design firm.  Boutelle, a gun enthusiast himself, invested capital to start up this new company on 1 October 1954.  The money came from the research and development budget of Fairchild.  This company would have an impact on the history and direction of the modern battle rifle in the U.S. beyond Sullivan’s and Boutelle’s expectations.  ArmaLite Corporation was born.  The Fairchild winged Pegasus would have a circle and cross hairs superimposed as the symbol of the new corporation.  ArmaLite was envisioned to be a “think tank,” not a small arms manufacturer.  The new designs were to be made but manufactured by a dedicated manufacturing facility.

Much success in life is timing, being in the right place at the right time.  Even more so, having an individual that knows how to spot talent and grab it.  While working on a prototype rifle, George Sullivan was test firing his design at the Topanga Canyon Shooting Range outside of Los Angeles where he saw and met a young man who was doing the exact same thing.  That young man was Eugene Morrison Stoner.

Shown is a Portuguese soldier with is A.I. AR-10. The Portuguese Army was well satisfied with the performance of the AR-10 and would have procured more if A.I. would not have cut off production.

Stoner was born in Gasport, Indiana on November 11, 1922.  His family would later move to California.  In 1939, Stoner worked for Vega Aircraft and with the U.S. entering World War II Stoner would serve in the Marine Corps as an Ordnance Specialist.  At the time of his chance meeting with Sullivan, Stoner was making dental plates and in his spare time he would design advanced rifles.  Sullivan was very impressed with the rifle Stoner was testing, later known as the M5 (it evolved into the AR-3), and hired him as the Chief Design Engineer at ArmaLite.  The AR-3 was granted U.S. Patent Number 2,951,424.

Stoner was a genius; well ahead of his time particularly in the firearms industry at that time.  In fact, radical would be the proper word.  In a world of tradition that required steel and wood, young Stoner would take his experience in the state-of-the-art aircraft industry and apply that technology to firearms development.  Using aircraft grade aluminum and synthetic materials in place of the traditional wood and steel, Stoner would create the lightest battle rifle in the world.  But was the world, particularly the U.S. Ordnance Corps, ready for it?

Stoner’s new concept, the AR-10 would deviate from tradition.  First, the AR-10 would be completely inline in construction.  Meaning the barrel, bolt, bolt carrier and recoil spring and buffer were directly in line with the shooters shoulder.  This reduces traditional muzzle rise and felt recoil compared to the traditional M1/M14 rifles.  This also makes the rifle firing in fully automatic that much more controllable.  Due to no drop in the stock, the sights had to be raised so the shooter could see through them; hence the carrying handle (third prototype) was born which would become an icon for Stoner designed weapons.

The first prototype rifle had the needed raised front and rear sight and was chambered for the 7.62x63mm (30-06 Springfield) cartridge.  The cartridges were fed from a standard BAR magazine.  The stock was a tubular stock with a butt plate added to the rear.  This rifle used the same direct gas system used in Stoners AR-3 rifle which we will discuss in more detail.

Shown is the bolt carrier group of serial number 1004 after firing 409 rounds. This picture is to depict the carbon fouling on the bolt carrier group.

The second prototype added a telescope sight, which was raised up to allow the shooter’s eye to align.  Stoner added a more conventional stock to the rifle.  The pistol grip was made from the same material as the stock and hand guards.  There were no iron sights on this model.  This model also differed in that it was chambered for the 7.62x51mm cartridge that was soon to be adopted as the standard cartridge for the U.S. military.

The third prototype was far more close to the finalized AR-10.  Many new features were added and also the gas system was altered.  The first thing you notice is the carrying handle on the upper receiver containing the rear sight as well as the raised front sight that is attached to a muzzle compensator.  The bolt was designed after the Mel Johnson designed multi lug bolt.  There are seven lugs as well as the extractor.

This rifle used a unique new gas system.  Although previously used on the Swedish AG42B and the French MAS44 and MAS49/56, the new part of the system was to be a gas cut off once enough gas was used to operate the action.  This reduced recoil as well as increased the service life of the moving parts of the rifle.

When the rifle would fire, the bullet travelled down the barrel until it passed the gas port.  Gas was tapped from the barrel into the gas port and pressurized a long gas tube on the left side of the barrel.  The gas tube entered the side of the bolt carrier group.  There a piston chamber was created between the back of an internal chamber in the bolt carrier and bolt.  The gas created an internal pressure, pushing the bolt carrier to the rear.  The cam pin is rotated by the cam path in the receiver unlocking the bolt as it moves rearward.  This also acted as the cut off for the gas once the bolt begins its rearward travel venting off the unused gas.  As the bolt carrier moves rearward the fired cartridge case is extracted and ejected from the rifle once the mouth of the case clears the ejection port.  Now the spring loaded buffer returns the bolt carrier group forward with the bottom two lugs stripping off the top cartridge from the magazine, feeding and chambering the round.  Then final movement locks the bolt into the barrel extension.

Perhaps the most disastrous moment in the history of the AR-10 and if any moment defined the failure in the U.S. trial was the catastrophic barrel failure of serial number 1002. This was caused by Sullivan’s decision to use his aluminum barrels with a SS rifle sleeve. Stoner was adamantly opposed to this course of action and he was right.

This gas system eliminated several heavy parts of the traditional piston mechanism including a heavy operating rod.  Recoil was drastically eliminated due to not having the mass of an operating rod and piston slamming into the shooters shoulder.  This decrease in weight of the carrier group increased accuracy as well.  To further lessen recoil in this inline construction rifle, a muzzle compensator was added.  This made recoil with the larger 7.62x51mm caliber round smooth and easy.

The 4th prototype took on more of what we see today in the design of the AR-10/AR-15.  The rifle has two receivers, an upper and lower held on by a front pivot pin and a rear takedown pin.  The receivers were manufactured from state-of-the-art 7075 T6 aircraft aluminum forgings.  The stock and pistol grip were manufactured from foam-filled phenolic resin, which was lightweight, very strong and impervious to the elements, unlike traditional wood.  The rifle was fed from an aluminum 20-round magazine.  For strength, reinforcing ridges were pressed into the sides of the magazine giving it the “waffle” appearance.  These magazines were intended on being disposable in combat.  Due to the light weight of the magazine, soldiers would be able to carry more ammunition in preloaded magazines compared to previous rifles.

Another outstanding feature of the design and one that would certainly decrease weight was the design of a barrel extension for the multi-lug bolt to lock into.  Unlike previous designs, a large chunk of metal surrounds the chamber to contain the pressures of the chamber and afford a location for the bolt to lock into.  The AR-10 barrel extension screwed onto the rear of the chamber and focused the pressure into a small area.  U.S. Patent Number 3,027,672 was granted for the barrel extension on April 3, 1962.

The rifle was very user friendly.  With the shooting hand, the thumb actuated the selector lever and trigger finger actuated the trigger and magazine release button.  The left hand actuated the bolt catch and cocking handle located inside the carrying handle on top of the rifle.  The left hand also loaded and unloaded the magazine.

Close up view of the muzzle compensator found on the early Hollywood rifles. The end is held on by a snap ring that could be removed with the tip of a bayonet.

The rifle appeared futuristic and broke with traditions of what a military rifle was supposed to look and feel like.  Too new for some and those were often the influential people making the decisions on procurement.  Many new designs were tried to make use of new materials such as the use of aluminum barrels.  That came to no avail but shows the type of research and development going on at ArmaLite.

In late 1955, the U.S. Army got their first look at the new AR-10.  It was demonstrated to high ranking officials at the Infantry School at Fort Benning and Headquarters, Continental Army Command at Fort Monroe.  It was ArmaLite’s hope to delay the selection of the new rifle to replace the M1.  The T44 (M14) and the T48 (FAL) had been tested for quite some time and the decision was close.  Using the 4th prototype as the base, 50 rifles were handmade.  The barrels were a controversial issue within the walls of the ArmaLite shop.  Stoner had highly recommended and fought to have standard military grade steel barrels used.  Sullivan however over-ruled his recommendations and they used aluminum barrels swaged around 416 SS rifled liners.

However, in the late 1950s a rifle was designed by Eugene M. Stoner at ArmaLite, Inc. called the AR-10.  ArmaLite was a division of Fairchild Engine and Aircraft located in Hollywood, California.  This revolutionary rifle was truly “Tomorrow’s Rifle Today,” that was more true than anyone knew back then.  Although it never had a chance to compete head-on with the M14 for the next U.S. infantry rifle due to Army politics, as well as the deep rooted thought of a rifle having to be made from steel and wood, the AR-10 did get noticed.  During its limited testing it was known to be the most accurate auto loading rifle made as said by the testers from Ordnance Corps.  Limited numbers of AR-10 rifles were manufactured in the Netherlands by Artillerie-Inrichtingen.  They were manufactured for Dutch Army trials as well as sold in limited numbers to some other countries including, Sudan, Cuba, Italy, Guatemala and Portugal.  As predicted, the M14 was adopted and the AR-10 was tossed in the Ordnance Corps scrap heap.  The requirement came down to scale the AR-10 down to a .22 caliber and the AR-15 was born.  The rights were sold for the AR-15 as well as the AR-10 to Colt’s Patent Firearms Manufacturing Company.  Colt went on to produce the AR-15 but ignored the AR-10 design.  That was left for other companies to capitalize on.  To trace the AR-10 lineage to today’s most advanced sniper rifle we must skip ahead nearly 30 or so years ahead to 1991.

In November of 1991, a Mission Needs Statement was drafted for an Enhanced Sniper Support Team Weapon (SSTW).  This was written by Lt. Col. David Lutz while serving as the Program Manager for Infantry Weapons at MARCORSYSCOM at Quantico, VA.  This documentation was an effort to restart a cancelled Designated Marksman Weapon program (DMR) based on the M14 which could not be made to do all the things needed in a logistically supportable package acceptable to the Fleet Marine Forces.  Its requirement document was weak because it totally lacked objectivity in doing a mission analysis or seeking other viable solutions.  At the time, the current SSTW was the M16A2 rifle.  This weapon supported the M40A1 sniper rifle in the two man scout sniper team.  The M16A2 SSTW was used to engage close-up targets and provide rapid fire suppressive fire if needed.  Some noted deficiencies were the M16A2’s poor interface with the soldier when having optics mounted, including night vision.  The current issue M855 ball ammunition did not meet the accuracy specifications of a SSTW.

USMC snipers firing the Mk11 Mod 0 on the range. Note the use of the suppressor as this is commonly used on the rifles in the field.

The enhanced SSTW would fill the role of a 0 to 600 meter intermediate range sniper rifle.  It would have ammunition interchangeability with the M40A1 7.62x51mm sniper rifle and it would have the ability to mount a sound suppressor.  Optics would be mounted in-line with the shooter’s eyes for a comfortable mount.  This rifle will also have to overcome current problems with the unit, direct, general, and depot support problems (availability and maintainability) long associated with the hand-built and Marine Corps customized M40A1.

Lt. Col. Lutz recalls that he knew of (5 each) Dutch NATO AR-10s that were in a bunker at Picatinny Arsenal from when he was stationed there during 1980-83.  So he had one of his successors, USMC Liaison Officer Maj. Dody Knootz, pick out one that shot the best and “temporary loan” it to them at Quantico.  Several modifications were made with the most significant being the carrying handle cut off and a weaver rail attached to the upper receiver.  The AR-10 had some of the improved M16A2 components added to it including the pistol grip and handguards.  All this was to make it look like and use A2 service rifle parts and training.  Additionally, they removed the AR-10’s faux muzzle, which incorporated a grenade launching spigot, exposed its skinny barrel and threaded muzzle.  Lutz recalls sending the upper to Phil Seberger to have a suppressor made & fitted to it.

As recalled by Lutz, as a concept demonstrator it was a success.  “When my general came out to fire it he brought with him his Australian Army Liaison Officer, a full colonel.  My general was reluctant to fire the weapon as I presented it to him, and handed if off to the Australian Colonel.  Offhand, the Colonel hit a steel gong at 100 yards with 20 of 20 shots (suppressed).  When he handed the rifle back to my general, he said “General, this is the finest rifle I have ever fired.”  When the General handed the rifle back to me, he said “Dave, you have a program.”  I guess the rest is history…”  Though the concept was sound, the Marines or big army were not ready for a semiautomatic sniper rifle, at least not yet.  So the AR-10 lay dormant once again until the early 1990s.  Even though the original DMR program failed, the STSW maintained life in the requirement and allowed Rifle Team Equipment builders at Quantico to produce more prototype M14 based variants as “interim measures.”  This eventually took on a “life of its own,” and an M14 based program eventually found traction as the M39 Enhanced Marksman Rifle (EMR).  However, the M39 is one of the weapons being replaced by the Marines recent purchase of M110s.  The M110 was inherently able to meet the STSW requirement for mounting of Night Vision without lose of zero, sound suppressor integration, M16 ordnance maintenance and training commonality, supply system commonality and cross-service weapon commonality.

The name Eugene Stoner, although not as well known as Browning, is just as significant in the history of the gun.  Stoner’s design is the longest service rifle in U.S. military history.  During Stoner’s ArmaLite days his goal was to develop 7.62x51mm weapons.  He was very fond of his direct gas system.  After the M14 was selected, the future was only in the smaller caliber round so Stoner went on to develop other rifles to fire the 5.56mm cartridge including the AR-18 and the Stoner weapon series.  He never quite forgot his AR-10.  In the early 1990s, Stoner went to work with C. Reed Knight, Jr., the president of Knight’s Armament Company.  The union spawned the rebirth of the AR-10.  This would be the SR-25 (Stoner Rifle-25 (15+10)).  This rifle would be an AR-10 but would take on the advancements of the M16A2 rifle and maintain 60% parts compatibility.

Right side of the M110 rifle receiver. Notice the ambidextrous bolt release above the magazine release as well as the ambidextrous safety lever. The U.S. markings are on the magazine well.

Released in the early 1990s, the SR-25 Match Rifle was equipped with a 24-inch Remington 5R match grade barrel – the same barrel blanks used on the M24 sniper rifle.  The heavy barrel was free floating with a fiberglass handguard.  The rifle was equipped with a flat top upper receiver with the Mil-Std 1913 rail and the receivers were made from aluminum extrusions.  The rifle was equipped with a 2-stage match grade trigger.  The bolt carrier group kept with the original AR-10 in that it was chrome plated and it also sported the captive firing pin retainer pin.  These were not mass produced rifles.  The uppers and lowers were mated together and had matching serial numbers to identify them.  They were specifically designed around the 168gr OTM Match cartridge.  Using this factory load, the ogive of the bullet set right on the rifling.  This is something match shooters want to accomplish due to not wanting the bullet to “jump” into the rifling thus maintaining control of the projectile right from the moment of chambering.  The original rifles used the standard “waffle” pattern 20-round magazine and later a steel magazine that looked more like an M16 20-round magazine in appearance.  The SR-25 was sold initially through commercial channels that funded R&D.  Every SR-25 was test fired at the factory and provided with a target.  Knight guaranteed that this rifle would fire 1 MOA or under with factory ammunition.  Gene Stoner would work with Knight up until his death in 1997.

The SR-25 quickly gained its reputation for precision accuracy and reliability and its versatility and benefits were appreciated right away by the special operation forces.  SOCOM liked the idea of having a semiautomatic rifle that held 20 rounds of ammunition and rivaled the M24 and M40A1 bolt action rifles.  They also liked that you could engage multiple targets in less than half the time they could with a manual bolt action rifle.

After more than 40 years, the AR-10 would have its day.  In May of 2000, the U.S. Navy and SOCOM adopted the SR-25 as their new Mk 11 Mod 0.  This would be follow by another contract in 2007 for 9.9 million dollars with the need from the Global War On Terrorism.  The Mk11 had some departures from the original design.  Designed to meet the SOCCOM requirement, the rifle was designed to fire the M118 and M118LR match grade 7.62x51mm NATO ammunition.  The Remington barrel was replaced with an Obermeyer barrel and was shortened to 20 inches and equipped with a mount for a quick detachable sound suppressor also developed by Knight’s Armament Company.  The 11.35-inch Rail Accessory System free floating handguard provided quad Mil-Std 1913 rails enabling attachment of any given number of accessories including night vision, lasers, tactical lights and bipods.  The standard M16A2 stock and pistol grip are used for parts commonality.  A flip up front sight was added to the gas block as well as KAC’s fully adjustable back-up iron sight was added.  The rifle was equipped with 20-round magazines, a Leupold Vari-X mil dot scope with detachable rings and a Harris bipod.  The Mk11 weighs 15.3 pounds unloaded and has an overall length of 45.4 inches.  The Mk11 would see action with U.S. Special Operations troops all over the world.  The weight of the complete Mk11 Mod 0 with the Leupold 3.5×10 scope & SIMRAD adapter, bipod adapter with LM type S Bipod is 13.7 pounds.