Why M-16 Rifles Couldn't Shoot in the Vietnam War (Part 1)

Between 1965 and 1969, more than one million American soldiers were sent to the harsh battlefields of Vietnam. Whether their participation in the war was justified is debatable, but there is no doubt that the soldiers there should at least have been properly equipped. Unfortunately, this was not the case. More than 40,000 American soldiers were killed by enemy fire and more than 250,000 were wounded. One of the reasons behind this tragedy was that the soldiers were equipped with a defective rifle that the command knew would fail the tests.

The cover photo shows a Vietnam War M-16 rifle and an M-60 heavy machine gun, both mounted on bipods, resting as US troops patrol the barren terrain of Hill 282, 12 miles south of Hue, in search of about 200 Viet Cong reported in the vicinity of the South Vietnamese rural area of Phu Loc. (Photo: Shunsuke Akatsuka/Bettmann Archive, via Getty Images)

Replacing the previous standard, heavier M-14, the M-16 was a rifle that was considered a great technical achievement in its first models. Unfortunately, bureaucratic hurdles and inadequate testing turned the M-16 into an unreliable weapon for soldiers in Vietnam. By 1967, soldiers using the M-16 were fed up with the problems they faced. Many soldiers wrote letters to their families expressing their concerns about the M-16, which came to the attention of the House Armed Services Committee. The Committee established a subcommittee to investigate the problems with the M-16 rifle. The Subcommittee, chaired by Representative Ichord, a Democrat from Missouri, produced a hearing record of nearly 600 pages. The hearings were led by Earl J. Morgan, the committee's attorney. This document, which received little press attention at the time and remains only a faint memory today, is a striking example of how ordinary bureaucratic errors can have devastating consequences.

Nearly a century before the Vietnam War, weapons designers made a startling discovery in wound ballistics: Small, fast bullets, when fired into human or animal flesh, caused more damage than large projectiles. While a large artillery shell could penetrate a human body, a small bullet could tear through muscle and tissue, causing horrific destruction. Early in the hearings of the House Armed Services Committee questioning the M-16 rifle, the chairman of the committee, Representative Ichord, a Democrat from Missouri, asked the designer of the M-16, Eugene Stoner, the reason for this paradoxical situation. Stoner's answer was revealed in the following eerie dialogue:

Ichord: A soldier told me that he shot a Viet Cong with an M-14 [uses a larger calibre bullet] near his eye and the bullet did not make a very large hole in the exit, but he shot a Viet Cong with an M-16 in the same place under similar circumstances and his entire head turned to pulp. This does not seem to make sense. You have a higher velocity but the bullet is lighter.

Stoner: When it comes to wound ballistics, a small or light bullet has an advantage over a heavy bullet. What this means is that the bullets are designed to fly in the air and do not follow the same flight path inside a hull that is close to the density of water or water. They are stable as long as they are in the air. If they hit something, they immediately destabilise. If you are talking about a 30-calibre bullet [such as a bullet used in the M-14], the moment it hits a human body, it can remain more stable, straight and stable in its post-collision progression. Because a small projectile has a low mass, it perceives the instability faster and reacts much faster. This is what makes a small projectile so useful in wound ballistics.

Forward-thinking Willard G. Wyman, Commander of the Continental Army Command, had asked Stoner to design a rifle to take full advantage of the profitability of smaller bullets. The AR-16, the forerunner of the M-15, had long used 30 calibre bullets instead of the 22 calibre that was standard for the Army. As early as 1928, an Army ‘Calibre Board’ had conducted shooting experiments in Aberdeen, Maryland, and subsequently recommended a shift towards smaller ammunition, perhaps in the 27 calibre range; but the Army, partly for technical but largely for traditional reasons, refused to give up the 30 calibre round, which it chose to describe then and for the next thirty-five years as ‘full size’.

A second discovery about weapons lay behind the design of Eugene Stoner's AR-15. In his studies of combat troops during World War II, SLA Marshall found that almost four-fifths of combat soldiers never fired their weapons during combat. This finding led the Army to take a closer look at the weapons used by soldiers.

It turned out that there was an exception to this rule for one group of soldiers: those carrying Browning automatic rifles (BAR) (M1918 Browning Automatic Rifle). These were essentially portable machine guns capable of firing continuous bursts of fire. (The rifles carried by other soldiers, the M-1s, were ‘semi-automatic’ and required a separate trigger press for each shot.) Within a battle group, fire would start with the BAR man and spread away from him. The closer a soldier carrying an M-1 stood to the BAR man, the more likely he was to fire. The explanation most often put forward was that the infantryman carrying a normal rifle felt that his actions were ultimately futile.

John Keegan said in his book The Face of War: ‘Infantry, no matter how well trained and well armed, how determined and ready to kill, remain unstable agents of death. Unless they are well directed centrally, perhaps badly, they choose their own targets, open and stop firing one by one, are distracted from their aim by the enemy returning fire, are distracted by the wounding of those close to them, succumb to fear or excitement, fire high, low or at wide angles.’ A normal infantryman cannot see the enemy clearly or have any idea whether he has been hit. In contrast, the BAR man has the feeling that he can dominate a given area, ‘hose it down’ in military slang, and destroy everyone present.

After World War II, the American army needed a change in infantry rifles. Officers demanded a new weapon that was lightweight, accurate and capable of firing fully automatic fire. In response to this demand, the M-14 rifle was developed in 1957. The M-14 was an automatic fire and lighter version of the previous standard M-1 rifle. Like the M-1, it used a 30 calibre round. But the biggest problem with the M-14 was that it was uncontrollable in full automatic fire mode. While the M-14 had the explosive power needed to propel heavy rounds, it was also designed as a lightweight rifle. This caused excessive recoil in the rifle. When firing full automatic fire, using the M-14 not only made aiming difficult, but also caused soldiers to suffer facial injuries and even nosebleeds due to excessive recoil. American soldiers trained with the M-14 in the early and mid-1960s and used the rifle in the early years of the Vietnam War.

The M-14 rifle was the product of an informal organisation known as the U.S. Army Ordnance Corps (OC) . This community consisted of weapons laboratories, private contractors and Army officials. The abbreviation OC will be used throughout this article. Army units responsible for small arms development were known by different names over time. The OC had this responsibility for more than a hundred years. The OC adopted a traditional approach to technology. In peacetime rifle competitions, the focus was on how well a weapon could hit a target at distances of 400, 500 and 600 yards. This point of view was defended by snipers and marksmen known as ‘pebble bellies’. Thomas McNaugher of the Rand Corporation, in a study of the M-16 rifle, stated that the M-14 ‘was developed with the assumption that aimed fire, sniper fire, was of the greatest importance in combat’. This assumption has remained valid for the US Army for almost a century since the adoption of the first rifle in 1855. McNaugher also explains the rationale behind the OC traditional approach. The Ordnance Department favoured tactics that emphasised slow and careful fire because of less wastage of ammunition and thus less pressure on supply lines and production facilities.

For the gunner's purposes, a large, heavy projectile was favoured because it was stable in flight and less susceptible to wind. Along with this marksman's point of view was an insistence on strict technical specifications. If a projectile did not leave the barrel at 3,250 feet per second, it was useless; if it was not fired in the Arctic and the Sahara and could not perform equally well in both places, it was unsuitable for army duty. These emphases had little to do with the experience of jungle warfare in Vietnam, where most fighting took place at distances of no more than thirty to fifty yards, and where speed and surprise were so important that it could often cost a soldier his life if he took the time to aim his rifle rather than point it in the right direction and open it automatically.

The OC was small-scale, parochial, old-fashioned. Its technical experts were divided into a number of sub-specialities: internal ballistics (concerned with the behaviour of the bullet before it leaves the gun), external ballistics (the flight of the bullet), wound ballistics and other areas. OC was further fragmented between technicians in the arsenals and research centres and military bureaucrats in the Pentagon. Historically, when a new technical possibility was presented, the first instinct was to reject it and stick to traditional solutions. Twice since the Civil War, American Presidents had had to force the OC to adopt new rifles from outside its own workshop.

There was also an air of intimacy in the relations between the OC and the rifle and ammunition manufacturers who supplied it. ‘Sole-source’ contracts that gave one company a monopoly on the army's business were not unusual. One of the most important of these was the contract with Olin Mathieson Corporation, a supplier of a type of gunpowder known as ‘gunpowder’ to the Army since the end of World War II, which proved to have a particularly important influence on the development of the M-16.

The OC had every reason to dislike the AR-15. It came from an outside inventor, and the OC threatened to replace the M-14, a product of its own arsenal system. This was not the rifle of a practical, down-to-earth and experienced person or a technician who was close to their point of view. It used a ridiculously small bullet by OC standards, a .22 calibre bullet, the kind kids use to shoot squirrels. In the early fifties, the US, OC, fought an uphill battle against the European governments in NATO, who wanted a small bullet to be recognised as the NATO standard. The OC was successful in its struggle to impose the 30 calibre bullet as the NATO standard, but it left a lot of bad will behind. Having won this battle, the OC was unlikely to surrender meekly at the same point on its own territory.

Around the time the M-14 was adopted as the army's standard, Eugene Stoner was completing work on the AR-15. Stoner was known as one of the great figures in the special call of small arms design. Like some other distinguished American rifle designers, including John Browning, the inventor of the Browning automatic rifle, who was forced to sell his weapons to foreign governments after being rejected by the OC, Stoner had never seen his models readily accepted by the Army. He was working for Armalite Corporation when he finished developing the AR-15.

‘The AR-15 overturned the traditional understanding of the rifle by combining a number of innovative features. Firstly, it used .22 calibre bullets, making it both lighter and capable of carrying more ammunition. This allowed soldiers to fight effectively for longer periods of time without running short of ammunition in combat. The rifle's low recoil made it easier to control automatic fire, while its light weight increased the soldier's mobility. Another important feature of the AR-15 was its exceptional reliability. Its almost jam-free mechanism, which could fire 600-700 rounds per minute, guaranteed the rifle's operability even under continuous fire. Thanks to innovations in the production method, the AR-15 was much more cost-effective than previous rifles. The forged pressed parts and the plastic material used both accelerated the production process and reduced costs. However, these innovations were met with scepticism by traditionalist military officials. The use of plastic material in the AR-15 raised concerns about the durability of the rifle, while the small-calibre bullet was considered not powerful enough. Despite these criticisms, the AR-15's designer, Stoner, argued that these concerns were unnecessary due to the rifle's reliability and firepower.’

The AR-15 was tested at three military bases in 1958. Reports were positive, but there were reservations from the ammunition establishment about the appropriateness of using such small calibre ammunition. To resolve differences of opinion, the Army commissioned an extensive series of tests at the Combat Developments Experimentation Command, known as CDEC, in Ford Ord, California. These tests lasted from autumn 1958 to spring 1959. The tests were not designed to follow the usual sniper model, but to simulate the conditions of small units in combat. In the tests, the AR-15 was paired with the M-14 and another light rifle manufactured by Winchester. The results, announced in May 1959, included the following findings:

a. If the total combat weight per man is equal to the weight planned for riflemen armed with the M-14, a squad of 5-7 men armed with the [AR-15] will have better accuracy and greater accuracy than the current eleven-man M-14 squad.

b. According to the surveys conducted by the troops participating in the tests, they preferred the [AR-15] for its light weight, reliability, balance and grip characteristics, and ease of recoil and climbing in fully automatic mode.

c. The qualities demonstrated by the prototype weapons in the light high-speed category indicate a general combat potential superior to that of the M-14. These advantages include ... lightness in the weight of the weapon and ammunition, ease of use, superior fully automatic firing capability, the accuracy of the Winchester and the functional reliability of the Armalite [AR-15].

The conclusion of the report was that the Army should develop a lightweight rifle ‘with the reliability characteristics of Armalite’ to replace the M-14. ‘Simultaneously with the adoption of a lightweight, high-velocity rifle,’ the report said, “serious consideration should be given to reducing the size of the existing squad” in light of the increased firepower of the new weapons. The repeated references to the ‘reliability’ of the AR-15 should be recalled in light of the weapon's unreliability after it was converted to the M-16 and sent into combat.

After the CDE tests, the Army accepted the theoretical ‘promise’ of the lightweight system but rejected it as a practical recommendation. Emphasising the importance of all rifles and machine guns using the same ammunition, the Army ordered the full production of the 30-calibre M-14.

However, the proponents of the AR-15 received the support of General Curtis Lemay, a respected arms enthusiast who was then Chief of Staff of the Air Force. Based on his interest, the Air Force conducted further tests and reviews, and in January 1962 declared the AR-15 the ‘standard’ model. The Air Force then took a step of enormous importance. On the recommendation of Armalite Corporation, which owned the design of the rifle, and Colt, which had the contract to manufacture it, the Air Force tested ammunition developed by Remington Arms Company for the AR-15. After the tests, the Air Force declared the ammunition suitable for its purposes. In May 1962, it ordered 8,500 rifles from Colt and 8.5 million rounds from Remington.

At this point, decisions about the rifle moved from the world of tests and specifications on paper to real combat. In 1962, at the urging of staff members who were advocates of the AR-15, the Department of Defence's Advanced Research Projects Agency managed to have 1,000 AR-15s shipped to Vietnam for testing by soldiers of the Army of the Republic of Vietnam (ARVN). The rationale was that the Vietnamese soldiers were too short and too weak to handle rifles with full-size ammunition. The reports were full of praise, especially about the exceptional reliability of the weapon. At one stage of the tests, 80,000 rounds were fired, but no broken parts were reported. During the entire process, only two spare parts were issued for all 1,000 rifles. The report recommended sending the AR-15 in bulk to South Vietnam as standard equipment for the ARVN soldier. But Admiral Harry Felt, then Commander-in-Chief of the Pacific Forces, rejected the proposal, saying that, based on the advice of the military, the use of different rifles with different bullets in the war zone would create a complex logistical problem. The Chief of Staff of the ARVN and the US Chief of Staff supported his decision.

Throughout 1962 and 1963, a series of tests, evaluations and counter-evaluations were conducted by the US military, the recurring theme of which was the lightness, ‘lethality’ and reliability of the AR-15. The results of a test conducted by the Department of Defence's Advanced Research Projects Agency were summarised by the department's auditor in September 1962:

Taking into account the higher lethality of the AR-15 rifle and the improvements in accuracy and rate of fire of this weapon since 1959, the overall squad killing potential of the AR-15 rifle is up to 5 times more effective than that of the M-14 rifle. ...

The AR-15 rifle can be produced with less difficulty, higher quality and lower cost than the M-14 rifle.

In terms of reliability, durability, robustness, performance in adverse conditions and ease of maintenance, the AR-15 is a significant improvement over all standard weapons, including the M-14 rifle. The M-14 rifle is weak in the sum of these characteristics. ...

It is much easier to train soldiers with the AR-15 than the M-14 rifle.

Within the standard load of weapons and ammunition, the AR-15 can carry three times more ammunition than the standard load of weapons and ammunition carried by a soldier.

Meanwhile, the Army Materiel Command, the home of the OC, was conducting its own evaluations of the AR-15. There was consistency in these, too. The Corps found little to like in the AR-15, and there were many technical objections against it. It had poor ‘sighting and night firing characteristics’; its penetration at long distances was also poor. The OC recommendation was to stick with the M-14 until a ‘radically’ better model based on advanced technology emerged from the recently initiated research programmes of the ammunition laboratories.

In early 1963, with the strong support of President Kennedy and Secretary of Defence Robert McNamara, Special Forces (better known as the Green Berets) requested and received permission to use the AR-15 as their standard weapon, as they needed light equipment for mobility and stealth. The Army's airborne units in Vietnam also received it, as did some agents of the CIA. As the AR-15 gained more and more followers among the troops actually serving in Vietnam, Secretary of the Army Cyrus Vance asked the Army's inspector general to re-examine the rationale and evidence that led the Army Materiel Command to reject the AR-15. His investigation revealed that the tests were clearly rigged. The M-14s used in the tests were all pre-selected, specially serviced and, most likely, the sights had been adjusted in advance for the tests for more accurate shooting. They were ‘Match Grade’ weapons (suitable for marksman competitions). The AR-15s were taken out of the box directly from the factory. The M-14's ammunition had also received special care. The inspector found that the various OC organisations had met in advance to discuss how to fix the tests. They decided to set aside a day to conduct the tests and then (according to the printed minutes of their meeting) to include in the final evaluations ‘only those tests... that would have a negative impact on the AR-15 rifle’. Within the Pentagon, the lines were more clearly drawn, with the civilian leadership of the Air Force and the Department of Defence (especially McNamara) supporting the AR-15, while the army ammunition establishment opposed it.

As the fighting in Vietnam intensified, in late 1963, the procurement of rifles began, with 19.000 rifles for the Air Force and 85.000 rifles for special Army units. In the name of efficiency, Robert McNamara appointed the Army as the central procurement agency for all services. It was at this point that the OC took possession of Eugene Stoner's AR-15; it declared it inadequately ‘improved’ and adopted it as the military version, calling it the M-16.

The first of several changes was the addition of a manual bolt closure, a handle that allowed the soldier to hand-tighten the cartridge after it refused to seat itself properly. The Air Force, which was to purchase the rifle, and the Marine Corps, which tested the rifle, strongly opposed this change. ‘During three years of testing and operation of the AR-15 rifle in all conditions, the Air Force has no record of any malfunctions that could be corrected with the manual bolt closure device,’ an Air Force document said. Worse, they said, the device would add cost, weight and complexity to the weapon, thereby reducing its greatest asset: reliability.

Years later, during congressional hearings, Eugene Stoner said he was always opposed to a shut-off device because ‘when you buy a cartridge that doesn't fit in the rifle and you intentionally chamber it, you usually buy yourself more trouble.’ Colonel Howard Yount, project manager at the Rock Island armoury in 1963, who bore the burden of explaining the ‘OC’ decisions throughout the hearings, was asked how this change could be justified. Not on the basis of complaints or previous tests, Colonel Yount said. It was justified ‘on the basis of guidance’. Where was the guidance from? asked a congressman. A direction from his superiors in the Army staff was all he could say. The widespread assumption was that the late General Earl Wheeler, then Chief of Staff of the Army, had personally ordered that the M-16 be rendered useless, largely because he had supported the decision to take the previous army rifles. Eugene Stoner said his only explanation for the Army's decision was that ‘the M-1, M-14, and carbine always had something for the soldier to shoot with’; [perhaps the Army thought this would give him a comforting feeling or something like that.]

The next change was to increase the ‘twist’ of the rifle's barrel (the spiral groove inside the barrel that allows the bullet to spin). The twist rate was changed from one in 14 inches to one in 12 inches. The greater twist allowed the bullet to spin faster in flight and therefore maintain a more stable trajectory, but it also allowed the bullet to be more stable as it entered the flesh, thus reducing by up to 40% the shocking ‘lethality’ that made the AR-15s so distinctive. The Army's explanation for increasing the ‘twist’ of the barrel was that otherwise the rifle would not have been able to meet all ambient testing. To qualify as ‘military standard’, a rifle and its ammunition had to perform equally well at 65 degrees below zero and 125 degrees above zero. Based on insufficient test evidence, an Arctic test team concluded that the AR-15 did not perform well in the cold weather portions of its test. Allegedly, bullets were wobbling in flight below 65 degrees. The army's response was to increase the ‘twist’ and thus reduce the ‘lethality’, although the rifle was expected to be sent to humid forests along the Mekong.

The last change was the most significant. Like the others, it was publicly justified by a lawful application of the specifications, but was apparently motivated by two other forces: the desire of some Army bureaucrats to discredit the AR-15 and the tendency to ignore the difference between meeting the specifications and producing a weapon that would perform reliably in actual combat conditions.

Weapons designers refer to automatic rifles as ‘resonant mechanisms’ in which several different cycles must work in harmony. One of the determining factors in the synchronisation of these cycles is the explosive properties of the gunpowder in the ammunition. Some gunpowders explode very quickly, while others build up pressure more slowly. Some decisions result from the detonation pattern; for example, the location of the ‘gas port’ or the appropriate cycle speed for inserting and extracting projectiles. Eugene Stoner had designed his AR-15 around a powder known as IMR 4475 (‘for the improved military rifle’). It was manufactured by Du Pont, who sold it to Remington for filling cartridges. It was made from nitrocellulose, sometimes known as gunpowder cotton. IMR 4475 ammunition was used in all early tests of the AR-15; it was the ammunition that proved its reliability in all field trials and was accepted by the Air Force.

In June 1963, the Army Materiel Command conducted tests at Frankford Arsenal that discredited the original IMR powder and revealed the most significant modification to the AR-15, a modification that, almost two decades later, remains the most difficult to explain. In 1981, when I was preparing the article (the Army Armaments Research and Development Command sent me an invitation to interview the technicians involved in the decision to abandon IMR 4475, which was later withdrawn. A spokesman for the organisation said : ‘These were decisions of the Army, so we think that the Department of the Army in the Pentagon should explain them.’ There is almost no one left in the Department of the Army who was in a position of authority at the time. The only official statements now available are those written in bureaucratic language by Colonel Yount when asked by Representative Ichord's committee to justify the actions of the OC).

The decision on the ammunition was based on detailed specifications known as the ‘technical data package’ that the Army prepared when it converted the rifle to the M-16. The data package included that the rifle's muzzle velocity should average 3,250 feet per second (fps) plus or minus 40 and that the pressure in the firing chamber should not exceed 52,000 pounds per square inch.

Where did these specifications come from? From Eugene Stoner, not from Armalite or any user or tester of the rifle. Stoner had based his design on an off-the-shelf commercial cartridge filled with IMR powder that never achieved the muzzle velocity the Army now specified. Some Army officials have claimed that the manufacturer advertised the round as having a velocity of 3,250 fps; if so, they preferred to believe the advertising rather than the actual performance of the round. In all of its previous tests, in the field trials that so excited the Air Force and Marine Corps, and in its successful performance in combat in Vietnam, the AR-15 produced a muzzle velocity with its original ammunition that was approximately 100 fps below the newly advertised level.

So what was the basis for the Army's decision? The Congressional committee tried a dozen different ways to get Colonel Yount to answer this question. The closest thing to an answer contained in the hearing record is the following paragraph from the Army's ‘Statement on Propellants for 5.56mm Ammunition’ submitted after Yount's testimony

➢ [ During the 5 .56mm ammunition programme, the Army could have chosen to reduce the specified velocity, thus avoiding the necessity of developing new propellants... This would have slightly reduced the range and effectiveness of the M-16 rifle. Instead, the Army chose to retain the original [sic] ballistic performance and use propellants capable of consistently meeting these requirements in mass production].

Once the Army had established these specifications, the outcome of its tests at Frankford Arsenal was predetermined: the original IMR powder would not work. To increase the velocity to 3,250 fps, it had to bring the chamber pressure very close to the limit. In February 1964, the Army sent a request to manufacturers to produce replacement gunpowder. A few months later, Du Pont said it would cease production of IMR, and Remington switched to Olin Mathieson, the Army's supplier of ‘gun powder’. By the end of 1964, Remington was loading only ‘gunpowder’ into the cartridges of the rifle renamed the M-16. (Another type of IMR powder, with different explosive properties than the original, was eventually produced as alternative ammunition for the M-16.)

‘Gun Powder’ was first adopted by the Army early in World War II for use in certain artillery shells. It differs from IMR in that it has a ‘double base’ (made of nitrocellulose and nitroglycerin) and in several other respects. Its most important difference is its explosive properties, since it burns longer and slower than IMR. In the United States, only one company produces gunpowder and sells it to the military. This company is Olin Mathieson, which received a contract for about 89 million cartridges in 1964 alone and made many more as the war progressed. More than 90 per cent of the cartridges used in Vietnam were filled with this powder.

After the Army made the decision to switch to gunpowder powder, it sent a representative from the auditor's office, Frank Vee, to have Eugene Stoner approve the change. Stoner had not been consulted about any changes to his rifle, not the bolt cap, not the barrel twist, not the powder powder, and he thought they were all bad ideas. He recalled his conversation with Vee to the convention committee as follows:

He asked me my opinion [about the specifications requiring gunpowder] afterwards. In other words, it was a rather strange meeting. ... I looked at the technical data package and he said, ‘What's your opinion?’ and I said, ‘I don't recommend that...’.

‘Well, they've already decided they're going to go that way,’ he said. He meant the committee. I said, ‘Well, why are you asking me now?’ He said, ‘Well, I'd feel better if you had approved the package.’

And I said, ‘Now neither of us feel better.’

(To be continued)

My other article closely related to this subject;

How the AR-15 Rifle Became America's Most Dangerous Weapon I leave the link below.

https://strasam.org/savunma/kara-silah-ve-sistemleri/ar-15-tufegi-nasil-amerikanin-en-tehlikeli-silahi-oldu-3404