The Only War We've Got

How the AR-15 became the M-16

What follows is adapted from a Institute of Defense Analysis report, Paper P-2192, DARPA Technical Accomplishments: An Historical Review of Selected DARPA Projects, Vol. 1, by Sidney Reed, Richard Van Atta, and Seymour Deitchman, February 1990. It focuses on Project Agile, a counterinsurgency program run by what was then known as the Advanced Research Project Agency (ARPA) in South Vietnam in 1961-1962. I have omitted the citations and edited a few phrases. Since the paper was commissioned by DARPA, it probably exaggerates the agency's role in the development of the M-16 infantry assault rifle, and it leans rather heavily on The Black Rifle: M16 Retrospective from Collector Grade Publications, Modern US Military Small Arms Series, Vol. 3.


ARPA bought a number of lightweight ArmaLite AR-15 rifles under project AGILE in 1961 and 1962 to evaluate in Vietnam. The very positive evaluation in August 1962 had a major impact on the DoD studies leading to a decision, in early 1963, to purchase AR15's in quantity for use in Vietnam, and eventually on the Army's adoption in 1967 of the follow-on M16 as its standard rifle.


The lightweight, high-velocity .22 caliber AR-15 rifle was originally developed by Eugene Stoner of Arma Lite division of Fairchild Industries in response to a request in 1957 by Gen. Wyman of the Continental Army Command. The background of this request came from earlier studies by the Army's Aberdeen Laboratory going back to the 1920's, and in the 1950's by Army supported studies by a contractor, the Operations Research Office (ORO), which indicated that a rapid fire, high-velocity, small-caliber weapon could be very effective at ranges at which rifles appeared most likely, from recent etperience in Korea, to be used in ground combat. It was also argued that lighter rifles could allow a soldier to carry more ammunition, and increase combat effectiveness.

While the ArmnaLite AR-15 had undergone a number of tests and had some support within the Army, initially it met with opposition from the Army Ordnance Corps. The Ordnance Corps favored the heavier, larger caliber, M14, which was designed for use primarily in the NATO theatre and had influenced the caliber and choice of and agreement on NATO standard ammunition. The semiautomatic M14's were being produced in large numbers in the late 1950's and early 1960's, and were expected to gradually substitute for several weapons: the M1 rifle, the Browning Automatic Rifle (BAR) and the carbine, as these were phased out of the inventory.

The AR-15 had also been taken on a "World Tour" demonstration in 1959 by Mr. Bobby MacDonald of Cooper MacDonald Company, affiliated with Fairchild.

In July 1960, an informal demonstration of the AR-15 was given to Gen. Curtis LeMay of the Air Force. This led to Gen. LeMay's recommendation for Air Force use of the AR-15 to replace their older carbines. After three tries, the Air Force was able to get approval for procurement of AR-15's in May 1962.

M16 rifle in 1964
The original service rifle as manufactured by Colt's for the US Air Force. I am reasonably sure that this was the model carried by Special Forces in Vietnam in 1964, when I traisped through the puckerbrush with the Green Berets. Though designated "M16", it was always called the AR-15. Generally a second clip was inverted and fastened to the first with Army green tape, so the rifleman could quickly reload, giving him 40 rounds before he had to scramble for more. "It is a little-known fact," as I was assured in basic training, "that the world is held together by green tape."

ARPA's project AGILE had a mission of rapid development of material for use by Vietnamese forces, and had set up a field R&D unit in Vietnam. The ARPA field unit reported that the small-statured Vietnamese soldiers were having problems with the M1 and other weapons they had been given by the U.S. due to weight and recoil. Bobby MacDonald, now affiliated with Colt Industries, which had bought out rights to the AR-15 from Fairchild, urged ARPA's project AGILE to test the lighter AR-15 in Vietnam. According to Stevens and Ezell [ The Black Rifle: M16 Retrospective, by R. Stevens and E.C. Ezell, Collector Grade Publications, Toronto, 1987]:

It wasn't long before the tireless Bobby MacDonald had convinced Col. Richard Halleck, on loan to the AGILE team from the Army, that the light, lethal but soft-recoiling AR-15 was just the rifle ARPA was looking for. By late summer ARPA had officially requested over 4,000 AR-15s to support a proposed full-scale test of the AR-15 in conjunction with special US advisor-guided units of the South Vietnamese Army. This request was denied, on the grounds that M2 Carbines was just as suitable for small-statured troops, and were available from storage. Undaunted, ARPA boiled the whole idea down to what they could afford: a limited range of tests in Saigon, in October 1961, with ten Colt AR-15s. The number of rifles might have been small, but the enthusiastic reaction of the Vietnamese and their American advisors alike who handled and fired the AR-15s was just as Bobby MacDonald had predicted.

Armed with these positive results, ARPA resubmitted its original request, clearly stating that the AR-15s required were to be used to arm special US advisor units and their Vietnamese allies only, and were not to be considered as a general issue item for regular U.S. troops.

This ARPA request came through Military Assistance Advisory Group (MAAG) channels. The MAAG had been trying to provide M-1 s, which came "free" as war surplus in Vietnam. In December 1961, Secretary of Defense Robert S. McNamara approved purchase of 1000 AR-15's for this field test. ARPA responded quickly, procuring the rifles and arranging for shipment. The test was to be under combat conditions, and involved experienced Vietnamese soldiers and U.S. military advisers. In August 1962, the AGILE field test report was in, stating that the Vietnamese much preferred the AR-15's and recommending that the AR-15 be considered for adoption by all Vietnamese forces, especially for jungle combat. Stevens and Ezell, in their recent history of the M16 state that "this (report) was the most influential yet controversial document so far in the history of the already controversial AR-15.... Immediately after the AGILE field test, the MAAG Vietnam requested 20,000 AR-15's. Apparently, the Army Material Command, which had absorbed the Ordnance Corps, agreed with the AGILE report that the AR-15 was more suitable for the small-statured Vietnamese troops. However, it was three years before AR-15's were made available in quantity for use in Vietnam, and nearly six years before they were made available to the Vietnamese forces.

A follow-on study, by C. Hitch of DoD's Systems Analysis Group, based partly on the ARPA field unit study, was issued in late September 1962 and was highly favorable to the AR-15. Stevens and Ezell describe the background:

Over this same period (summer 1962) ARPA staffers back in Washington had introduced the ubiquitous Bobby MacDonald to others in the OSD's Systems Analysis Directorate. A demonstration for all interested OSD personnel was arranged wherein AR-15s and Ml4s were fired in comparison with the standard assault rifle of the communist world, the 7.62x39mm AK47. Within this framework the AR-15's light weight, low recoil and controllability on automatic fire appeared particularly impressive.

A comprehensive OSD study of the history of service rifle caliber reduction was soon in the works. Stating with the .276 Pedersen round of the nineteen-twenties, OSD analysts worked their way through the ORO studies and BRL's small caliber, high velocity (SCHV) reports of the fifties, and concluded with the results of their own comparison of the .223 caliber AR-15 rifle with the M14 and the AK-47. A report of their findings was sent to Secretary McNamara on September 27, over the signature of OSD's Comptroller, Charles Hitch. Abandoning all pretense that the AR-15 was suitable only for small-statured Vietnamese, the Hitch report stated:

The study indicates that the AR-15 is decidedly superior in many of the factors considered. In none of them is the M14 superior. The report, therefore, concludes that in combat the AR-15 is the superior weapon. Furthermore, the available cost data indicate that it is also a cheaper weapon. Although analyzed less thoroughly, the M14 also appears somewhat inferior to the MI rifle of World War 2, and decidedly inferior to the Soviet combat rifle, the AK-47, which in turn, was derived from the German "Sturmgewehr" of World War 2.

Because of the contradictory views about the AR-15, the White House requested and the Secretary of Defense ordered a reevaluation of the Army's rifle program, to be carried out by January 1963. The Army's Chief of Staff had, in fact, already started such an evaluation. The Army's January evaluation report was a qualified negative, commending use of the AR-15 for airborne and special forces, but not for NATO. However, rumors of bias led the Secretary of the Army Cyrus Vance to request the Army's Inspector General (IG) to investigate. The IG reported a finding of bias.

Cowboy: interpreter, warlord, one more casualty

After some further discussion with his systems analysts, who pointed out that an Army flechette-firing rifle, the Special-Purpose Individual Weapon (SPIW), was in development and might soon supersede the AR-15 and M14's, Secretary of Defense McNamara directed in January 1963 that there be no more M 14 production after FY 1963, noting that there were many M14's in the inventory. The Secretary of Defense also applied M14 production funds to purchase AR-15's for the Army special forces and airborne units. The Army assumed procurement responsibility for the AR-15 soon after, and agreed to a "one-time" buy of 8.500 AR-l5's, which later became 104,000, of which 19,000 were for the Air Force. A formal AR-15 project office and interservice technical committee was set up by the Army, with guidance by Secretary of Defense that changes to the AR-15 were to be minimal and at least cost in order to exploit the advantages of commercial development. Also there were no RDT&E funds for the AR-15. Deputy Secretary of Defense Gilpatrick further advised the Army, "to avoid the cost, delay, and manpower difficulties of quality control, parts interchangeable and acceptance test standards programs of various rifle procurements." However, the Army wanted a number of changes, such as manual bolt closure, bore twist, and, importantly, ammunition. The Army wanted to use more potent ball-powder ammunition, apparently in order to obtain larger lethal ranges approaching NATO requirements. The Air Force and U.S. Marine Corps disagreed with these changes; however, they were instituted, partly because the Secretary of Defense insisted on getting a single rifle for all three services, and because of the pressures of Vietnam. In 1964, the Army type-classified the AR-15 as the experimental M16 EX1 for issue to U.S. troops. In the spring of 1965, the M16's were in use by U.S. airborne troops deployed in Vietnam. In July, Gen. William Westmoreland requested 100,000 M16's for all American combat troops in Vietnam. However, the Commander-in-Chief Pacific (CINCPAC) and the Joint Chiefs of Staff (GCS) disagreed with this request, giving as reasons priorities, difficulties with logistics, and the superiority of U.S. weapons in Vietnam. The intervention of a senator who visited Gen. Westmoreland in December 1965, cleared the way to satisfy this request. In September 1966, new XM16EI's were issued to U.S. Army units in Vietnam. In December 1966, Secretary of the Army Resor officially informed Secretary of Defense McNamara of the results of the Army's small arms weapons systems (SAWS) program, aimed at evaluation of small arms to the 1980's -- stating that the XM16E1 was generally superior, needed a few further changes, and that the SPIW was unlikely to be useful in the foreseeable future, and certainly would not be available for Vietnam.

>However, as large numbers of M16's began to be used in Vietnam, a number of serious problems began to be reported, in particular the rifle's tendency to jam under heavy use in combat. These led to visits to the field by Army and Colt experts, and also to several Congressional investigations beginning in early 1967.A systematic field test was conducted by the JCS' Weapons System Evaluation Group (WSEG) with help from the Institute for Defense Analyses (IDA), to investigate the M16 problems. Some of these problems were traceable to a lack of maintenance manuals and instruction, and others were eventually found to be due to excessive chamber pressure associated with the ball-type propellants imposed by the Army. which caused a more rapid firing cycle, and also to corrosion associated with the propellants and the lack of interior plating of the chamber and barrel. These problems were considered broadly due to the rapid rate of introduction of the rifle directly into use, without concurrent RDT&E, and the corresponding lack of proper support by industry and the Army. Partly also, some difficulties could be associated with the use of more powerful ammunition, in the desire to extend lethal range in a weapon originally designed for use at limited range. Some of these problems, e.g., maintenance manuals, were dealt with quickly; others have been overcome in a gradual "product improvement."

In early FY 1968, the M16 was made available to the South Vietnamese Army by the Secretary of Defense. In July 1968, the U.S. Military Assistance Command, Vietnam (USMACV) published an analysis of the results of arming the South Vietnamese Army army with the M16, which reconfirmed the advantages of size, weight, rate of fire, ballistics, and logistics and credited its introduction with a significant improvement of operational capability, morale, and esprit de corps. Many of the problems of the M16 have been gradually overcome by evolutionary improvement and change, and the M16 is now the standard rfle for the U.S. Army. The The M16 has also been sold, and is in production worldwide. Stevens and Ezell state:

As summed up at an April 1971 ARPA Small Arms Conference by Dr. W.C. Pettijohn, author of numerous studies on the analysis of small arms effectiveness:

The M16 has proven itself to be a superior rifle and has been accepted as such on a worldwide basis. It also has potential for mass production in the event of an emergency. There are no weapons currently that can be considered a competitor. Government efforts to develop a successor will proceed slowly. The conference forecasts six to eight million M16 rifles being produced during the next ten year period at a cost of two to three billion [dollars].

Active, direct American military involvement in the Vietnam war ended in 1973. Later Defense Intelligence Agency estimates were that among much other ordnance, the U.S. supported Army of the Republic of Vietnam (ARVN) and the Cambodian Army had been forced to abandon roughly 946,000 serviceable AR-15, M16, XMl6E1 and M16A1 rifles to the victorious North Vietnamese Army (NVA). In the mid-1980s, when many of these weapons began to appear on the international small arms black market, the M16 became the most widely distributed 5.56mm rifle in the world.

>However, problems remain in meeting NATO requirements for armor penetration and also in satisfying requirements of the U.S. Navy with the M16. In fact, the U.S. adoption of the M16 as its standard rifle appears to have disregarded previous U.S. commitments to NATO. Joint Army-Marine Corps efforts were started in the late 1970's under the Joint Services Small Arms Program (JSSAP) program to develop a larger caliber rifle and penetrating ammunition for use on future battlefields expected to include large numbers of armored vehicles.


The AR-15, predecessor to the M16, was already for sale worldwide and had been decided on by the Air Force as a procurement item when ARPA purchased some for test in Vietnam. Thus ARPA did not undertake a technological development, but a test under field conditions which was timely and highly appropriate for the AGILE mission. The train of subsequent events, which led finally to acceptance of the M16 by the Army, can be definitely traced to the impact of the early ARPA-supported test results. However, ARPA's originally stated motivation, to quickly supply the Vietnamese troops with a weapon more suitable for their size and for the short ranges usual to jungle fighting, was not achieved. It took nearly six years for the Vietnamese army to get the M16. The difficulty in getting Army acceptance of the AR-15 at the time was partly due to the fact that the Army had extensive commitments to the M14, which had just gotten into large-scale production, after some difficulties, and had been accepted by NATO, and partly to availability of surplus M-1 rifles in Vietnam. Partly, also, ARPA's interventions on behalf of the AR-15 aroused considerable resentment in Army circles.

The problems with the M16 that occurred in Vietnam can be traced to a mixture of DoD overconfidence in the original product, and the changes instituted by the Army without concurrent R&D and testing. The lack of R&D was due to a DoD top level decision, apparently in the belief that the AR-15 was a finished product, and that R&D would get in the way of expeditious procurement. In spite of the fact that DoD had previously agreed to standards for lethal ranges with NATO allies, the M16, which does not meet these standards, was adopted as the principal U.S, Army rifle. Some of the troublesome changes by the Army seemed to be due to a desire to approach these NATO standards. [In 2020, the M-16 and variants are in service with several NATO countries, including Canada, Britain, Denmark, Estonia, France, Greece, Latvia, Lithuania, Netherlands, Poland, and Turkey, as well as the US.] Apparently, NATO may accept something like the M16 as a secondary assault rifle. However, expectations continue that in a NATO war longer lethal ranges and gredter armor-penetrating capabilities will be needed, and R&D efforts continue to provide U.S. forces with a suitable rifle. ARPA recorded outlay for two purchases of first 10 and later 1000 AR-15 rifles and their shipment at a cost of about $500,000. This does not include expense of the AGILE field office in Vietnam in connection with the tests. A rough estimate of dollars expended for the M16, by the U.S. and others, is between $2 and $3 billion.

A Vision So Noble

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