M16 Origin

All posts tagged M16 Origin

The story of the AR-15 / M16 is one of Persistence & Continued Evolution.

Introduction of the AR-15

In 1958, the ArmaLite Division of Fairchild Aircraft Corp. introduced the first prototype of what it called the AR-15 (“AR” for ArmaLite Rifle).  It was a scaled down version of ArmaLite’s bigger, select-fire AR-10, and instead of shooting the full-power 7.62x51mm NATO cartridge, it shot a.22 cartridge.  The AR-15’s .22 chambering resulted in low recoil, making it easy to consistently shoot accurately in semi-auto, and easily controllable in fully automatic, while still providing terminal ballistics acceptable for the battlefield.  With a 20” barrel and a loaded 20-round magazine, the AR-15 weighed just more than 7 pounds.  This was a big departure from traditional U.S. infantry rifles like the M1903 Springfield, the M1 Garand and the M14, all of which were larger, longer, heavier and for the M14, arguably uncontrollable in full-auto.

The more agile, low recoiling and controllable AR-15 looked like the perfect solution for a U.S. military that wanted a smaller, lighter rifle for anticipated close range combat environments.

Colt Steps In.  Birth of the M16.

In ~1959 ArmaLite sold the rights to the AR-15 rifle designs to Colt, who designated it the M16, and aggressively marketed the design to branches of the US Military.  (Even as far back as the late 50s and early 60s Colt offered a semi-automatic version of the AR-15 to civilians.)  Full-scale military tests of the M16 platform were conducted during the first half 1962 in South Vietnam.  Successful feedback in performance and terminal ballistics resulted in U.S. Air Force adoption of the M16, and small scale testing by U.S. Navy SEAL Teams.  Based on U.S. Air Force findings, the rifling rate of the standard 20” barrel was changed from 1-in-14”, to 1-in-12” which improved accuracy, but may have resulted in reduced lethality.  At some point not long after, (early-to-mid 1960s), the M16 was adopted as the standard infantry rifle by almost all branches of the U.S. Military.

Problems Arise On The Battlefield.


US M16A1

On Feb. 28, 1967, the XM16E1 was standardized as the M16A1 rifle.  It was also the height of a jamming epidemic.  Reports from the battlefield included widespread chronic failures to extract, with cartridge cases seized in the chamber of the gun.  This condition rendered the rifle inoperable, and required a time consuming clearing process that left the soldier extremely vulnerable during the time required to perform the operation.  For too many U.S. soldiers in Vietnam, this became a catastrophic, fatal flaw.  As a result, many troops at the time didn’t want the M16.  Confidence in the platform was at an all-time low.

When word of the problems with the M16A1 reached U.S. Congressional leaders, the House Armed Services Committee of the 90th Congress established a Special Subcommittee in May of 1967 to investigate M16 Rifle malfunctions.  Throughout the summer of 1967, this three-member Special Subcommittee, chaired by Representative Richard Ichord (D-Mo.), diligently researched root cause of M16 malfunctions.

The M16A1 Rifle Comes Into Its Own.

In October 1967, the “Ichord Committee” published a 51-page report on M16 extraction failures.  Root cause was identified as the gunpowder used in the ammunition.  Specifically, the gun powder resulted in high chamber pressures and significant carbon fouling.  (In layman’s terms, gun powder residue built up enough in critical areas of the gun to seize what should have been moving parts.)

Remediation included changes to the gunpowder used in M16 ammunition and chrome chambers, which were more resistant to powder fouling.  These recommendations were immediately put into action and soon after reports of malfunctions dissipated.  The M16A1 rifle began to prove itself in the violent battles of the A Shau Valley in 1969 and the incursion into Cambodia during the summer of 1970.  Battlefield reports then indicated the M16A1 as a highly effective infantry weapon and it served U.S. Armed Forces through the 1980s.

Continued Evolution.

The M16A2

In 1980, NATO member nations formally adopted the 5.56×45 mm cartridge as the chambering for all NATO rifles.  In November 1983, the U.S. Marine Corps adopted an improved version of the M16A1 chambered for the 5.56×45 mm NATO round.  The rifle is called the M16A2.  In addition to being chambered for the new round, significant M16A2 improvements included improved rear sights, a brass deflector, a heavier barrel, 1:7” rifling and a “BURST” setting delivering three rounds with every trigger pull instead of full-auto.  The U.S. Army follows the Marines Corps adoption of the M16A2.

Colt’s XM4: The Army’s M4 Carbine, and the M16A4

For Special Operations Teams Colt experimented with shorter and lighter “Commando” variants of the M16 platform as far back 1966, but in 1984 they focused on an M16A2-based carbine for wider use.  That carbine was designated the XM4 and combined the compactness of a 14.5” barrel and collapsible stock  from the “Commando” series with the new 5.56×45 mm NATO chambering and other M16A2 improvements, like “BURST”, the brass deflector, 1:7-inch rifling, a bayonet lug and the ability to mount the M203 grenade launcher.

Although at first equipped with M16’s signature carrying handle, the XM4 was later produced with a removable carry handle and a flat-top upper receiver, used for easily mounting optical sights.  In September 1994, the Army standardized it as the M4 Carbine and began distributing it to combat units. Not long thereafter, Colt began to produce M4 carbines equipped with the Knight’s Armament Rail Accessory System in place of the standard forward hand guards.

This forward rail system allowed easy mounting of more accessories like tactical lights and laser aiming devices.  The flat-top M4 Carbine with rail system proved so successful that a new a full length rifle with the same features was soon adopted as the M16A4 Modular Weapons System (manufactured by Colt and FN).

The Rest Is History…

Today, M16 variants, like the M16A2, the M4 Carbine, and the M16A4 Modular Weapons Systems remain in service, equipping all branches of the U.S. Military.  They are the rifles protecting our shores, helping ensure freedom for others, and fighting the global war against terrorism.  AR-15 / M16 variants are also currently used by many Law Enforcement Agencies across the country.



The M16 earned what will likely be its greatest distinction on May 2, 2011, when a variation of the M4 Carbine (the HK416) was used to kill terrorist leader, September 11 mastermind, Osama Bin Laden during the heroic SEAL Team raid on his compound in Abbottabad, Pakistan.

So from the first field tests in the early 60s, through a tenuous time in 1967, to making history in 2011, variations of the M16 platform have served the American military for 50 years – persevering, evolving and continually improving along the way.  With 50 years of service, the M16 platform remains in service longer than any other rifle in U.S. military history.  It has also been named No. 2 Top Combat Rifle of All Time by the Military Channel.

50 years of history have proven that the AR-15 / M16 platform is relatively small, fast, light weight, easy to shoot and battlefield effective.  Yet perhaps its greatest asset is its ability to be quickly and easily tweaked to fulfill a variety of different missions.  The basic modularity of the gun, the ever popular flat top and forward rail system and the extensive variety of available accessories allow the AR-15 / M16 to be configured to satisfy just about any requirement.  It is the platform’s ability to easily change configuration that has kept it in service for so long, and it continues to evolve today.

(Special Thanks to American Rifleman, Heckler & Kock USA and Colt for much of the background information and pictures.)