The History of the AR-15 and 5.56×45 NATO Cartridge

Table of Content

The 5.56×45 Origins and AR-15 Initial Reviews (1950- 1960)
The AR-15 Wading through the Muck (1960-1962)
Questionable Results and A Breakthrough (1963)
More Modifications to the AR-15 (1963-1967)
Problems in Vietnam (1965- 1970)
The 5.56×45 and NATO (1967-1980)
Moving Towards Modernization (1969-2000)
The 5.56×45 Modern Era (2000-Present)
The 5.56×45 Going Forward

Of course, if we are going to discuss the 5.56×45 NATO cartridge, the story is going to lean heavily on the weapons platform that is chambered to fire the round. This means we are going to take a long look at the AR-15 and subsequent M-16 and all of the rifles that sprung from these initial designs. The majority of the story is going to focus on the rifle more so than the ammunition, but they are intrinsically linked together.

Like the politics and controversial testings of this cartridge and its rifle platforms, the information that is out there can be exhausting to wade through. In this article, we have done our best to provide the most accurate information and dates on this topic in hopes to provide you with a clearer picture of this rich history.

The 5.56×45 NATO has one of the most interesting and controversial histories of any rifle caliber that we can think of in modern warfare. Not only did it vastly change the landscape of small arms, but it had profound impacts on world stage politics and modern warfare. Grab a cup of coffee and enjoy this story as much as we have.

The 5.56×45 Origins and AR-15 Initial Reviews (1950- 1960)

We are not going to follow the full genealogy of the 5.56×45 NATO back to its origins. Instead, we are going to begin this story with the .222 Remington Cartridge. The .222 was the first rimless cartridge to be produced for civilian use in the United States in January of 1950. And while there is a lot of history leading up to the design of this cartridge, the simple reasoning for mentioning it here is that it is a huge leap towards the design of the .223 Rem and eventual 5.56mm round (click here for our ammo comparison tool).

During this period in the late 1940’s through the 50’s, a lot of research was being undertaken with small caliber and small bore weapons with high velocities. One of the major reasons for this line of research came from the theory that lighter bullets at higher velocity may be more effective than larger and slower projectiles and will be better suited for semi to fully automatic firing.

It was also during a time, after the conclusion of WWII that an obvious replacement was needed for the M1 Garand that incorporated much larger round capacities as well as selective firing between semi and fully automatic settings. Smaller cartridges also meant that more ammunition could be carried by infantryman without weighing them down, a concept gaining even more importance and relevance in Vietnam.

We also have to remember that at this period, the technology in smokeless powder was not as advanced as it is in modern times, where we can launch much larger bullets at speeds of 3,000+ fps. This was not the case at the time and cartridges being used were not as effective in combat situations at 300+ yards.

The US military looked for a solution to this problem by opening up a competition for firearms manufacturers to develop and test a new infantry rifle platform in the late 1950’s.

ArmaLite, a small department in the Fairchild Engine & Airplane Corporation, began designing and producing small firearms in the mid-1950’s and employed one of the more famous small arms designers, Eugene Stoner. And yes, the AR designation stands for ArmaLite, not assault rifle, which many seem to think.

In 1957, ArmaLite entered the competition to produce a new combat rifle for the US military, though they entered into the competition slightly later than other models. Gene Stoner and his team at ArmaLite produced the AR-10 but eventually lost the contest to the T44 rifle which would later be modified and renamed the M14 (7.62×51 NATO). The AR-10 did provide a working blueprint for the AR-15, which eventually was modified to the M16, the eventual standard for the US Infantry. The AR-10 did fair well enough in the competition that it was recommended to be scaled down to chamber a smaller caliber cartridge.

The resultant selective fire AR-15 was chambered for the smaller .222 Remington round. Gene Stoner, with the assistance of Robert Hutton, realized that the .222 Rem casing could not handle the amount of pressure generated to gain the wanted ballistic performance. As a result, the .222 special was developed. This round provided the power offered by the .222 Rem Mag but with a lengthened case which better suited feeding in semi-automatic weapons. In 1959 the .222 Special was renamed the .223 Remington, which many of you will realize is the civilian version of the 5.56×45 NATO.

During this time frame, the AR-15 is put through a multitude of field tests to test the .22 caliber firearms effectiveness. There are mixed results in the reliability and effectiveness but positive. In fact, for the last round of tests, the results of the published Rifle Squad Armed with a Lightweight High-Velocity Rifle, the praises are so high that it is pushed as a potential replacement for the M1 Garand rifle (7.62×51 NATO).

Perhaps the biggest reason for the US government not being sold on the AR-15 was a major test of the rifle by the Infantry Board and School in Fort Benning in 1958. Stoner was heavily involved in the training of the users, and all accounts show that the rifle performed well. There were improvements that needed to be made to the rifle, but most experts in the field of small arms that had encountered the AR-15 felt they were small hurdles that could easily be fixed. The board even determined that the AR 15 was more reliable than the M14, which would eventually replace the M1 Garand in the US army. Even so, Dr. Carten, Army Chief of Small Arms R&D, deemed the rifle inferior to the M14.

After failing to make any meaningful contracts for the AR-15, ArmaLite sells the license for the AR-15 to Colt Firearms who immediately begin making modifications to the rifle.

The AR-15 Wading through the Muck (1960-1962)

We are going to spend a significant amount of time on this section of history for the AR-15 and .223. It is quite the story of politics, feet dragging, and ineptness that at times seems to be akin to a court drama of renaissance Kings. One of the main reasons we want to dive into a bit more detail here is to give you a better sense of the chaos that surrounded the AR-15 and its navigation through a myriad of different military departments and even Congress.

While now holding the rights to the AR-15 as well as bringing on several key designers of the rifle from ArmaLite including Robert Freemont and Gene Stoner, modifications are made to the rifle and an extensive tour to market the rifle takes place. They even gain several contracts to smaller countries during this period. One of the key improvements of the AR-15 made by Colt includes a malfunction rate of only 2.5/1000 rounds in Aberdeen D&PS tests in November of 1960. This is a vast improvement compared to past tests in the late 1950’s at Ft. Benning, though the validity of those earlier results will be questioned.

To begin showing their improvements, they request new ordnance testing of the rifle but are denied by Dr. Carten, as the current head of the department does not believe there is a military requirement for the rifle. As you remember, he was responsible for the horrendous recommendation of the rifle at the Fort Benning proving grounds only a few years earlier.

Luckily, Colt had friends in high places including then Vice Chief of Staff of the United States Air Force, General Curtis E. LeMay. During a 4th of July party thrown in honor of the former President of Fairchild ArmaLite, Richard Boutelle, who is a longtime friend of General LeMay also happens to be in attendance. LeMay is given the opportunity to fire the AR-15 at several watermelons and is very impressed with the performance.

General LeMay agrees to champion the AR-15 as a replacement for the aging M2 carbines that were currently in use by the USAF. This breakthrough also urges Colt to utilize Copper-MacDonald Corp to represent Colt in getting the AR-15 tested and approved by the United States government as well as mediating large contracts for the rifle.

With higher brass getting behind the AR-15, Dr. Carten, who ordered the AR-15 unsatisfactory only a few years earlier, approves further testing for the rifle for use in the USAF. An inquiry by Congress on why the Ordnance Corp, headed by Carten, seemed to be the only group not sold on the AR-15 is also put into motion.

For the next several months and into 1961, the USAF tests the AR-15 with several reports published on the efficacy of the weapon including its marksmanship school’s report; Evaluation Report of the Colt-Armalite AR-15 Automatic, caliber .223.

Several .223 cal AR-15s are sent to Lackland Air Force Base where they are tested and compared to the M2 carbine, which is currently in use, as well as the M14. During these tests, users of the AR-15 show two-fold increase in expert ratings compared to the M14. General LeMay, who is fully behind the procurement of the AR -15, highly recommends that the rifle is selected by the USAF Air Staff committee and procured at a rate of 19,000 rifles per year.

During this period, LeMay is promoted to Chief of Staff of the USAF but still runs into resistance in bringing the AR 15 into use for the USAF in replacement of the M2 that would continue to plague him through 1962.

Gen. LeMay was briefed shortly after his request by the Department of Defense that funding of the 19,000 AR-15 rifles is not feasible for several reasons. One is that switching an entire branch of the military to a new caliber rifle is not desirable. Another huge reason, and perhaps the true reason so many government officials were against the AR-15, was that there was a large surplus of M2 carbines and ammunition that would be wasted. No elected official wants millions of wasted tax dollars on their record with elections coming up. That’s as true in 1961 as it is today.

So the story now moves to the Office of the Secretary of Defense. During meetings with General LeMay and several key staffers in the OSD, the final result is that the procurement of the rifles is not approved. As we just stated, the main reason is they do not see how they could pass such a large sum through the budget. This is an old dilemma for the military and the US government. While the experts in the military see the usefulness of the new rifle and its advantages over currently equipped weaponry, it all comes down to money and how the government, specifically Congressmen and Senators, will look to the public on such wasteful spending. When not being engaged fully in a public war, this would be near impossible to swing without major blowback.

There was another interesting development for the AR-15 and its .223 round during the year of 1961, and that was due to the start of Project AGILE. AGILE was directed by the US Department of Defense and was initiated to begin developing methods of warfare in counterinsurgency, specifically in Southeast Asia. Robert MacDonald, who was in charge of gaining contracts through the US government for the AR-15, pitches the merits of the rifle to a leading US official in the AGILE Project. This is interesting as a lot of the testing is going to occur in the South Pacific as well as Southern Vietnam, where we now know a major conflict was brewing and where the AR-15 or more specifically, the M16 would see heavy use.

Testing of the AR-15 and the .223 round in South Vietnam through the AGILE project submits their report (Test of ArmaLite Rifle, AR 15) and high grades are given for the system. Very small recommendations for improvements are made and include a rougher texture on the handguard and improvements to the cleaning rod. Through 80,000 rounds fired, the report states that only two replacement parts were ever needed. In the review, they state that the AR-15 is the top shoulder fire rifle for their purpose and purchase several rifles. Only a few months later, the Advanced Research Projects Agency, which was in charge of Project AGILE, requests 4,300 AR-15 rifles but are denied by the Office of the Secretary of Defense for the same reason Gen. LeMay has been continually denied; a surplus of the already circulated M2 carbines and its .30 cal ammunition.

General LeMay continues to probe, better yet, annoy government officials over the induction of the AR-15 into the USAF into 1962. It is even reported that then President, John F. Kennedy, personally tells the General to stop “badgering” the Army about the rifle.

As you have probably already deduced, even JFK cannot keep LeMay from getting his rifles. Though his request for 19,000 AR-15 rifles for general use in the USAF is denied, he attempts to get around this by proposing the rifles be used for special force units and requests only 8,500 rifles. He receives the funding almost immediately after the proposal is submitted. Most likely in the hopes that the granting of his request would sate his want of the rifle. While not exactly what he wants, the AR-15s are now on the way to the USAF and will be listed as an official part of the USAF inventory in 1962.

We also want to take a moment to discuss the larger impacts the AR-15 had on the military. The feet dragging and ineptitude that was uncovered from the attempts to get the AR-15 into service showed a lapse in the military doctrine of introducing and procuring new weapons. While not fully responsible, the AR-15 and its path through induction had to be part of the reason for the Secretary of Defense, Robert McNamara, to overhaul a lot of the organization and departments of the Army. Few other rifles and their associated cartridges have resulted in such wide sweeping changes in military protocol.

Several other key milestones in the rifle and .223 round occur during the year of 1962. Remington officially submits the .223 cartridge to the Sporting Arms and Ammunition Manufacturers Institute (SAAMI), and The American Rifleman publishes an article on the AR-15. The article does have some negative comments on the platform including the inaccuracy of the rifle and cartridge. They make a key observance and recommendation to fix this issue by changing the rifle twist rate from 1-in-14 inches to 1-in-12 inches, which is far from the last time the rifling twist is debated.

At this point, with the USAF gaining funding for the AR-15 for special force units as well as the praise coming out of South Vietnam, from the AGILE Project the US Navy orders a small number of the rifles for testing by its SEAL teams.

With such high praise for the AR-15 becoming more widespread, the newly appointed Secretary of the Army Cyrus Vance pushes to reassess the M14 program with the thought of replacing it with the AR-15. However, funding, as well as logistical issues, is a major concern of the OCSA (Office of the Chief of Staff) as well as the inaccuracy of the rifle in cold weather as pointed out by the American Rifleman article. The OCSA also points out that changing the rifle twist, as recommended by the American Rifleman article, will reduce the lethality of the firearm.

This stance by the OCSA is interesting given that two days prior in September of 1962, a famous report, now known as the Hitch Report, was generated by System Analysis office of the OSD and titled, A Comparison of AR-15 and M14 Rifles. In this report, the AR-15 is touted as the superior rifle and cartridge compared to the AK-47 and M14. In fact, in this report, the currently deployed M14 is labeled as inferior to the AK-47.

With the Hitch Report out, high-level officials, including President Kennedy, begin questioning why the AR-15 has been stalled in its production and disbursement in the military. This leads to intense trials with the rifle and .223 cartridge by the US Army through the year into 1963. During these trials, the OSD (Office of the Secretary of Defense) budgets in the purchase of 19 million rounds of .223 ammunition.

All of this testing and renewed interest in determining the most suitable rifle for US military infantry all came to a head in a series of reports by various departments in the US military and government agencies. Several of these reports include the Comparative Evaluation of AR-15 and M14 Rifles by Aberdeen’s D&PS, The Comparative Evaluation of AR-15, M14, and AK-47 rifles and M79 Grenade Launcher, by The US Army Arctic Test Board, The Rifle Evaluation Study, by the CDC’s Infantry Combat Developments Agency, and the CDCEC’s report, Comparative Evaluation of Rifles. There are several other reports that came out around the same time at the end of 1962, and all of them give high marks for the rifle, though there are several issues which we look into below.

While the AR-15 has high marks in several categories especially in the groupings of shots fired when compared to the M14, just about all of these reports still point our key issues with the rifle that keep them from recommending it for general military use. Several of these are water in the bore, deficiencies’ in reliability in cold environments, and night firing capabilities. The main conclusions from all of these reports are that the M14 is far from the most effective rifle, but it should remain in service as the main infantry weapon until a better alternative is found. They state that the AR-15 needs some more work but is a good choice to begin implementing into light, special force units, but they do not recommend anything further.

Questionable Results and A Breakthrough (1963)

With so much promise in 1961 and 1962 for the rifle, it turns in the opposite direction as 1963 rolls around. As at the end of 1962, the publishing of reports testing the AR-15 and other rifles in use or being developed for infantry continue to pour in.

At the start of 63’, the Army publishes several reports on their testing of the AR-15 and M14 and come to some interesting and questionable conclusions. According to their reports, the .223 does not meet NATO standards of the time and is inferior to the M14 at ranges over 400m. These reports also state that the AR-15 suffers from malfunctions at an alarming rate and they were not able to match the performance reported by the AGILE project in Vietnam nor other recent tests of the rifle and cartridge.

Looking back, it brings a lot of questions up on how there could be such varying results on the rifle, and since being put up for a potential weapon from the US Military, all results coming from the US Army have it performing poorly while other departments and tests show much more promising results. Of course, there were reasons for concern in all reports, but nothing to the extent as seen in US Army reports.

Because of this, Army Secretary Vance ordered an internal investigation into the Army’s findings and the extent of manipulation that went into making the AR-15 seem inadequate is quite astounding.

It was shown that the personnel undertaking the testing skewed the tests heavily in favor of the M14. This included accuracy testing and grouping data with the AR-15 on fully automatic while the M14 remained on semi-auto. Match grade M14 rifles were used as well as match grade ammunition for the rifle during accuracy testing. The AR-15 was also tested in less than ideal weather conditions while the M14 was not and it was even found that data that gave a poor outlook on the M14 was completely omitted from the report. It was quite obvious from the investigation that nothing was fair in the comparison of these two rifles.

These results helped push the initial contracts for the AR-15 and branches of the US military, and it also spelled the end of production of the M14. The USAF initial request for 80,000 AR-15 rifles is accepted by the Department of Defense, and even the US Army requests 85,000 AR-15 rifles, but it is more of a way to appease the brass before the SPIW project is complete and they can move away from the AR-15.

More Modifications to the AR-15 (1963-1967)

The .223 Rem ammunition that was currently in use had some issues and was pointed out at a meeting between representatives from the US Air Force and Army. It is stressed that the Remington .223 cartridges in use suffer several deficiencies, one of which is light powder charge. It is agreed upon that the rifle and its ammunition need a standard military specification to adhere to.

The US Army Weapons Command and (WECOM) and the US Army Munitions Command (MUCOM) begin to address some of the design flaws of the rifle and soon after the Office of the Secretary of Defense requests a joint effort of the military branches to draft a set of requirements for improvement of the AR-15 and the .223 Rem ammunition. And in typical government fashion, the cost of these requirements should be kept to a minimum.

A new department is formed, Office of Project Manager for AR-15 Activities, and is headed by LTC Harold Yount. This department was formed in the hope of having a more centralized area where developments can occur and assist all of the various branches and departments that would be heavily involved in the modifications of the rifle and its ammunition. As we just discussed, there was already demands for improvements and the development of standards for the rifle and the cartridge. It’s also important to introduce LTC Yount, as he will be a major name in the coming years of the rifle’s service in Vietnam where it was met with tremendous blowback.

Along with the Project Manager for AR-15 Activities, the TCC (Technical Coordinating Committee) which would be responsible for accepting or rejecting proposals for changes to the rifle and ammo is formed.

For the .223 Rem, the OSD officially classifies the round as the 5.56mm M193 Ball. This cartridge has specs of a 3,250fps muzzle velocity and a 52,000psi pressure limit and is loaded with the IMR 4475 powder and fitted with a 56gr projectile. Three of the major ammunition manufacturers do not submit bids for this cartridge, as there are major design flaws in their opinions. The government would eventually change the specs slightly to allow an extra 1,000psi of pressure in the casing.

It is also approved during 1963, that the rifle twist be changed from 1:14 inches to 1:12 inches. A slam-fire problem also kept presenting itself, and the military and ammunition manufacturers argue heavily over primer sensitivity and the feasibility of increasing the sensitivity. The inability to agree leads to the suspension of acquiring 5.56mm ammo for a short period.

Another point of contention in design changes of the AR-15 is a manual bolt closure device. For the bolt-closure device, the USAF is strongly opposed to the design while the US Army deems it necessary. The USMC appeared to be indifferent and will accept it if it shows to improve function and reliability of the rifle.

Even in the midst of these arguments, the government wants to push for production of the rifles due to issues with Colt and their threats to shut down assembly without a contract in the immediate future.

By the time production rolls around, there are major modifications to the rifle. We already mentioned changes in the twist rate, a lighter firing pin is used to combat the slam fire issue, a bolt closure device is included for the Army XM16E1 rifle, and a t-shaped charging handle among other design changes. All of these changes lead to a final contract with Colt worth $13,671,195 in early 1964 and are the turning point from the AR-15 to the M16! The USAF would receive an additional 19,000 M16 rifles (no manual bolt closure device) while the US Army and Marines would receive the XM16E1.

In 1964, there is still a concern with the propellant used in the M193 Ball rounds. The IMR 4475 powder was having issues with generating the desired muzzle velocity. A potential replacement for this powder, the WC846 propellant by Olin was generating the wanted velocity consistently, but also generating incredibly high cyclic rates in the rifle. The fix for this issue was to simply raise the recommended rate of the rifle to 900 rpm.

An important note here is that Colt investigated the use of this powder and found that it increased the gas port pressure. It was dismissed and thought the increased gas pressure might improve the functioning of the rifle, which will turn out to be quite the opposite, but we will come back to this in just a few moments. Another type of powder that would be considered, tested, and eventually loaded into the M193 Ball ammo is the CR 8136 propellant manufactured by DuPont.

Colt, which is still the only manufacturer and supplier of the M16 rifle, runs into issues with the quality of their manufacturing in early 1964. The assembly line is shut down for a short period due to inspections citing inadequate quality control. And this shouldn’t be much of a surprise given the number of weapons they were now responsible for producing for the military and especially since tensions were beginning to mount in Southeast Asia. On top of all this, they were still gaining smaller contracts to foreign entities as well.

While the US Military and Government felt having secondary producers was necessary, the issues they had with Colt over the matter kept them from awarding contracts to other producers. They were also wary of a lack of uniformity they would encounter and the general feeling that they needed what they could get, as fast as they could get, for as little money as possible and it resulted in them leaning solely on Colt for the time being.

Other changes in the design of the M16 continues through 1965 which include changes to the design of the buttstock, which is rejected by the military because of the decrease in space for holding cleaning materials. Ironically, this space for cleaning materials will not seem to matter in Vietnam as the majority of soldiers were not even issued proper cleaning tools for their rifles early in the conflict. This change does lead to a new material for the buttstock, and further testing of the material is warranted.

We will touch on the initial reception of the rifle by troops in Vietnam shortly, but during the same period that this was occurring, the new Chief of Staff of the Army, General Johnson decided that any new changes to the Army’s rifle program were not necessary given the performance of the M16 in the field. Before that decision, the US military had initiated a program to examine and test several other light rifles such as the AR-18, Stoner 63, and CAR-15 for the replacement of the M14 and M16.

With any semi-auto and automatic weapon, accurate tracer rounds are essential. Aberdeen’s D&PS publishes the report Engineering Test of Cartridge, 5.56-MM, Tracer, XM196. This test was undertaken to determine several of the physical performance traits of the potential tracer round such as accuracy, cook-off temps, penetration, and general performance with the rifle. The conclusion of the report recommends that the XM196 be considered for use with the M16 and XM16E1 rifles.

During the period from 1965 to 1967, there is also a lot of research and testing being carried out regarding the propellant used in the M193 and M196 rounds. The initial IMR 4475 powder has already been taken out of the equation with the WC846 and CMR 170 powders taking its place, though still in question. Several other powders are brought in for testing as well. Key reports such as the Fifteenth Memo Report on AR-15 Rifle-Ammunition System: Investigation of Alternate Propellants For Use in 5.56mm Ball and Tracer Ammunition done by Frankford Arsenal and the Effect of Ammunition Variables on Acceptance Testing of XM16E1 Rifles by Colt show that the WC846 propellant produces a high cyclic rate, high gas port pressures, and fouling though the fouling does not appear to cause any issues with the performance of the rifle. In fact, the overall performance of the cartridge loaded with WC846 gains high marks. A new propellant, EX 8208-4 is recommended from former study as a suitable replacement.

Also in 1966, Colt presents the TCC with a new buffer assembly designed by Foster Sturtevant that includes multiple internal sliding weights. This new buffer is superior to the currently used system in several ways. The first is that the buffer prevents light strike misfires, which is what it was designed to do, but it also solves a major problem of the rifle unknowingly. This is that it greatly reduces the cyclic rate of the rifle because of its increased weight. In short order, Colt begins producing M16 rifles with the new buffer designed by Sturtevant. This is a major step in making the rifle more reliable and occurs after the debacle with malfunctioning weapons in Vietnam, which we will look at in detail shortly.

At the start of 1967, the XM16E1 is officially reclassified as the “Standard A” rifle for the military and takes on the new designation, M16A1. This reclassification occurs in the midst of the conflict in Vietnam.

Problems in Vietnam (1965- 1970)

In 1965, the now labeled M16 (more specifically, it is the XM16E1 with the forward assist bolt closure device) and 5.56 round (M193) were being deployed in Vietnam with the 173rd Airborne Division.

Initially, the reaction from soldiers towards the rifle was excellent with the ranking officers in the region stating that the rifle is far superior to the M14. It is also stated that the M16 is performing well enough that the issues being brought up about the weapon are to be dismissed.

In the Spring of 1965, General Johnson visited the American forces in Vietnam, and he encounters a multitude of officers requesting that their squads be outfitted with the M16 rifle. While there will be major issues to crop up with the rifle in the field, it can’t be argued at how well the design, especially the weight and dimensions, is suited for warfare in Vietnam.

In fact, it is so highly regarded initially by commanding officers and the higher brass that General Westmoreland, eventual Chief of Staff in the Army, bypasses the chain of command to request 170,000 M16E1 rifles for the Army and Marine Corp. This request, in the midst of growing escalation of events, need to be accelerated to the point of doubling Colt’s monthly production rate which should already make you begin questioning the quality of the rifles coming off the line.

The decision to bring in more M16 rifles to Vietnam is not just though necessary by the Generals, the majority of commanders, both Army and Marines, agree that the M16E1 is a better choice than the M14.

A few months later in June of 1965, a new contract is signed with Colt that is worth over 45 million US dollars. This new contract calls for a little over 800,000 M16E1 rifles and 28,580 M16 rifles. From this point, it is clear the US military and government are all in on the M16 and 5.56mm for better or for worse.

It did not take long for reports to begin seeping out that the M16 was suffering from malfunctions in the field, specifically with the bolt and bolt carrier seizing. Of course, this information was not released to the public and was not even widespread in the upper branches of the US military at the time. It is still important to note, as issues with the rifle would soon become rampant and lead to a lot of turmoil at home.

At the start of 1966, the TCC compiles all of the test data on the latest version of the XM16E1 and concludes that the malfunction rate in testing is not serious enough to interfere with combat operations in the field, but it is enough to warrant corrective action. By February of 1966, all US Army units are now training with the XM16E1.

Besides those initial reports coming out of the rifle seizing, all seemed to be going smoothly with the M16 in Vietnam. The USARV evaluated military tactics in Vietnam and published their report, Evaluation of US Army Combat Operations in Vietnam (ARCOV). In this report, the M16 was highly recommended for soldiers in the Vietnamese environment, especially when compared to the M14. It was lighter, and the extra ammunition greatly increased a squad’s overall firepower. The automatic feature of the rifle was also highly regarded as it presented a multitude of advantages to the squad on initial engagements with the enemy and in the case of ambushes.

By around June of 1966, reports were flooding into Yount’s office regarding the malfunctions of the M16 in the field. The main concern was the failure encountered when ejecting spent cartridges from the chamber. This trend continued through 1966 and 1967, and by the Spring of the latter, the failures of the rifle in the field became public.

With numerous and widespread reports of these malfunctions coming in at alarming rates, General Westmoreland calls in for technical consultation. This consultant group is made up of several representatives from WECOM and Colt and even Colonel Yount. Back home, Robert Fremont and a team inspect rifles that are sent back from Vietnam that encountered malfunctions. From this technical inspection, the most glaring faults that they find are an almost total lack of maintenance (Best Gun Oils Tested) and cleaning of the firearms. The quick fix for the issue is small teams to visit units and instruct proper cleaning and maintenance protocols.

• The unofficial report outlines several faults that would have caused the malfunctions;
• Carbon buildup in the chamber, bolt, and bolt carrier group
• Overloading of magazines
• Oil and grit inside magazines
• Lubricated ammunition
• Failure to replace worn or broken extractors and extractor springs.
• Shortages of technical manuals, cleaning equipment, and repair parts
• A general lack of knowledge among soldiers, both commissioned and non-commissioned

Regardless of the issues, General Johnson orders that the XM16E1 rifle will be adopted as the standard Army rifle and will be reclassified as “Standard A.”

At this point, a lot of questions should be coming to mind. Colt had repeatedly failed to meet the demand needed for the rifles, some cases it was extreme enough that M1 Garands had to be issued to troops. Even still, the military was requiring more and more rifles by the month from Colt to keep up with the demand of escalating conflict in Vietnam. Huge numbers of malfunctions and failures were continuing, and these are not dumb people in charge. They had to have been aware that there were bigger issues than simply failure to clean the rifle. One can not help but think that everything was too far along to make halt production and make major changes or to develop a new weapon in time for deployment. A poor excuse when the blood of American soldiers is at stake.

In hindsight, it is easy to simply look at these issues as they are, a step towards the modern AR-15 and 5.56×45 NATO rounds, but these problems encountered during its introduction to the military in Vietnam was a major concern. Reports found hundreds of deceased American soldiers in Vietnam with jammed rifles at their sides. It also raises the questions of how there could be such as disconnect between troops on the ground and the men making decisions back home for so long. Especially when such failures in communication lead to the deaths of American soldiers. In reality, it was all a culmination of choices in the preceding years to procure a rifle quickly and cheaply, and it cost a lot of young men their lives in a foreign country.

So what steps were taken to alleviate such problems?

For a quick fix, Col. Yount begins an investigation into the rifle’s finish and chrome plating of chambers. Also, he emphasizes advance shipments of repair parts and cleaning kits.

With the technical consultant teams submission of their report to the higher brass, they recommend the following actions be taken immediately;
Instruction manuals on the care and cleaning of the M16 be published and distributed at company or rifleman level
There should be emphasis placed on command supervision training of maintenance
New troops are required to receive a minimum of two hours M16 maintenance training during their first week in Vietnam
Immediate USARV inspection and repair of all M16s on hand by divisional direct support maintenance teams and elements of the 1st Logistics Command.

While this is a logical step to take given that the rifles in service were not being maintained properly, it still was not addressing design issues with the firearm itself. We did mention previously that Colt began producing rifles with the new buffer which would lower the cycling rate of the rifle and lower malfunctions. They also began looking into manufacturing chrome plated barrels which would help cut down on corrosion and make it easier to clean for the infantry in the field.

In May of 1967, the troubles encountered with the M16 become public through photos published in the Paris Match which shows deceased US soldiers accompanied with field stripped rifles. The implications being these soldiers were desperately trying to rectify the malfunctions of their rifles while under enemy fire. This led to an extreme and warranted reaction from the public which led to immediate congressional investigation.

Within the next month, the Ichord Subcommittee is formed and visits Vietnam to examine the reliability of the M16 rifle. One of the key members of this subcommittee is a retired Army Colonel E.B Crossman. After the committees visit, Crossman submits his report, Report of Investigation of M16 Rifle in Combat, to the committee. Within this report he states that the manual bolt closure, which was argued on its merits, has ended up being invaluable in the field. He also finds that upon interviewing 250 interviews, approximately half have experienced malfunctions with their M16. The reasons for the malfunctions include worn extractors and extractor springs that are not being replaced and a lack of critical pieces of cleaning equipment including cleaning rods and brushes. He also finds that nearly half of these soldiers prefer the M14 solely for more confidence in reliability when in combat. The report spurs on further investigations into the rifle and ammunition design and manufacturing.

The results of these hearings lead to dismissals and resignation from several key players in the history of the AR-15/M16 and its 5.56mm ammo including now promoted Colonel Yount, Deputy Secretary of Defense Vance, and Secretary of Defense Robert McNamara

In July of 1967, the newly appointed Deputy Secretary of Defense Paul H. Nitze issues a memorandum directing a technical evaluation and field study of the M16. This evaluation is initiated in hopes of determining whether any major deficiencies exist, and if so, recommend corrective action.

Following this directive, in the fall of 1967, the Ichord Committee released its final report and findings, Report of the Special Subcommittee on the M-16 Rifle Program of the Committee on Armed Services. (Washington DC: United States Government Printing Office. October 17, 1967). Some of the major complaints from this report include key points we have already discussed, including production practices by Colt as well as the military’s handling of procuring these rifles quickly as well as money management. It was also pointed out that the ammunition most commonly used in the M193 (WC846) played a role in the rifle failures. As we have discussed, the WC846 had some issues from the beginning that the military, Colt, and the ammunition manufacturers were aware of such as high gas chamber pressure and fouling. The powder did provide the wanted muzzle velocity, and because it was also the powder used to load 7.62 NATO rounds, there was plenty of it around. Once demand for ammunition increased, it was the most logical choice. Given the high gas port pressures created by the Ball powder as well as the gas piston operating system design, gas residue was able to enter the action which was partially responsible for the numerous extraction malfunctions. We should note that the WC846 propellant was modified in the early 1970’s and designated WC844, which is a propellant still used for the M193 Ball and M855 Ball 5.56×45 NATO rounds in present day.

As big of a tragedy as this issue was, it did shed light on the shortcomings and oversight in the development of small arms in the US, and it did lead to more stringent quality control efforts put in place by the US Government and Military institutions.

A later report, M16 Rifle Survey in the Republic of Vietnam, was published in May of 1968. In this report, it is stated that there are still enough extraction issues to cause concern, but the rate has dropped since the improved distribution of cleaning equipment and training in maintenance of the firearm. There are still alarming numbers including the number of soldiers who have not received training before arriving in Vietnam, the number of soldiers who have never zeroed their rifle or have zeroed it in the last three months, and failure to test fire weapons before entering into combat.

Other modifications such as chrome plated barrels and chambers and new buffer system are also helping reduce the number of failures. Overall, troop confidence in the rifle is beginning to recover from the previous two years. This trend of improvement would continue throughout the rest of the conflict.

The 5.56×45 and NATO (1967-1980)

Up to 1967, the AR-15 and M16 along with the 5.56mm M193 were still relatively confined to use in the US military. As we know it today, the M16 and the 5.56×45 NATO round is prevalent in a multitude of allied nations. This section, regarding dates, is going to overlap a little with the previous and forthcoming section. We still felt it was necessary to give the process of the 5.56mm round becoming a NATO standard its own section.

In the NATO Standardization Meeting in 1967, the British propose that a study be instituted to determine the desirability of accepting the 5.56mm as an additional standard NATO round. All nations vote in favor of the study at that time though many reservations were still held over the cartridge, especially the current M193 round used by the US.
An example of this reservation can be seen with the Danish Army in 1973. The Danes began testing selective fire rifles to replace the currently used M1 rifles. They use quite a few different rifles, and the M16A1 actually tops all other firearms in the group. Even so, they are hesitant to bring in the 5.56mm Ball without adoption by NATO. Because of this, they end up going with a rifle that finished 10th in their testing to meet this compliance with NATO standards.

At a snail’s pace, the NATO trial candidates finally begin technical testing (weapons and ammunition) in April of 1977. Tests occur throughout several training grounds throughout Europe.

In June of the following year, field-testing for NATO weapons and ammunition entries begins at several training grounds throughout Europe. Included in the set of candidate firearms is the M16A1 from Colt, which is loaded with the XM777 Ball and XM778 Ball Tracer rounds. These tests continue through November of 1978.

Fast forward all the way to May of 1980 and NATO’s International Test Control Commission finally releases their final report of the previous three years of technical and field testing of rifle and ammunition candidates. There are three major conclusions that come from this report;
The 5.56mm round is suitable and should be adopted as the second standard for NATO small arms calibers.
The Belgian made SS109 cartridge should be used as the basis for the standardization agreement.
There is no recommendation for a specific light rifle.

With over a decade of battle experience and who knows how many tests in control settings, the 5.56×45 managed, no required, a promotion and in 1980, NATO agreed to make the 5.56×45 the standard for infantry military service. We now have the 5.56×45 NATO, which is still the standard for several militaries around the world. And though the M16 is not selected as a standard weapons platform for the 5.56mm NATO, it’s magazines are eventually standardized.

The 5.56x45mm round that is adopted by NATO is quite different from the M193 Ball rounds that have been used by the US military up to this date. The two major differences were the Belgian SS109 round used a 62 grain projectile rather than a 55 grain projectile used by the M193 round. The SS109 also had a hardened steel penetrator core that allowed deeper penetration at a distance. This new cartridge would eventually gain the designation of the M855 cartridge and will be used for modern 5.56mm rifle platforms.

Moving Towards Modernization (1969-2000)

During this period, both the rifle and the ammunition became and remain a staple in the shooting world. A lot of changes came about as well as the number of options for both the rifle and ammunition. Because of this, we would be looking at a couple of pages if we were to attempt to list everything that occurred. So, we are just going to summarize some of the major events that occurred between the years of 1970 and the turn of the century.

During this period, a lot of research and experimentation occurs with the casing material such as aluminum and steel casings rather than the traditional brass casings. Later on, a lot of emphasis is placed on using non-toxic components in the cartridge.

In July of 1969, new contracts are awarded to Colt as well as GM-Hydramatic for M16A1 rifles. The first lots of rifles from GM-H are found to have severe flaws including defective bolts and bolt carriers. Many of the rifles also fail accuracy and endurance tests. Luckily, the quality control for manufacturing of these rifles has picked up due to recent incidents.

In 1969, Aberdeen began testing a new 30 round magazine for the M16A1 and published its findings in the report, Initial Production Test of Magazine, 30-Round, for M16A1 Rifles.

A contract for self-production of the M16 rifle is reached for the South Korean Government as well as a co-production agreement for the Philippine government is awarded in 1973. Additional sales are made throughout the rest of the decade to Jordan, Haiti, Indonesia, Thailand, Zaire, Ghana, Israel, Chile and several more countries. At this point, the M16A1 is becoming one of the standard military rifles of the world.

In 1977 testing at Aberdeen confirms that the XM777 and XM778 are indeed “superior” in performance to the issued M193 and M196. As we saw in the NATO section, the XM777 and 778 eventually fall by the wayside with the introduction of the new Belgian rounds that are adopted by NATO.

By the end of 1979 and into 1980 there is a trend in the various branches of the US military requesting improvements to the M16A1 rifle. Well, all except the Air Force who seemed to be quite content. The Marine Corp opens up talks with Colt in the Fall of 1979. The Navy and the US Army Infantry School also make it known that their current rifles have several flaws that need improvement. All of them conclude on their own that they do not want to revert to the M14 and there are not many promising projects anywhere near ready for deployment.

The Naval Surface Warfare Center (NSWC) releases its report, Improved M16A1 Rifle Instrumented Tests and Results, in the summer of 1980. This test took a pair of M16A1 rifles with heavier barrels and improved, round forearms and pitted them against two standard M16A1 rifles with all four having a 1:12-inch twist. The results are pretty dramatic with the heavier barrel with the improved forearms showing an increase in handling performance as well as accuracy in both fire settings.

In 1981, major changes came to the M16A1 rifle. Fifty experimental M16A1(PIP) are ordered for testing. These rifles are later designated the M16A1E1 and are tested heavily throughout the year. These experimental rifles include several improvements that have been requested from the various military branches. Some of these improvements are the following:

• 3-round burst mechanism
• Strengthened forearm and buttstock
• Longer Buttstock
• Round and symmetrical forearm
• Heavy barrel with 1:7-inch twist for XM855 and 856 ammunition
• Fully Adjustable 800m rear sight

In 1982 at Picatinny, Vince De Siena and MAJ Dave Lutz (USMC) begin working on another modification of the M16A1E1 rifle. They machine off the carrying handle of an M16A1 upper receiver and attach a commercial Weaver scope rail for the attachment of optics (Best Red Dot Sights). This is a big step towards modern tactical rifles that are seen in today’s militaries. This modification of the M16A1 is pitched as an additional modification to be added to the PIP program. These modifications would eventually be integrated into the M16 and result in the modern M16A4 rifle in the late 1990’s.

It is also during this year that the Department of Defense begins to show interest in a small carbine version of the new M16A1E1 model which in subsequent years will become the M4 Carbine.

Continued Testing of the new model of the M16A1E1 goes very well and results in the rifle being reclassified to the M16A2. The M16A2 has 12 major modifications that are distinct from the M16A1.

• The M16A2 now has a muzzle brake/compensator rather than a flash suppressor.
• A heavier barrel with a 1:7-inch twist.
• Checkered and strengthened buttstock
• Square front sight
• Longer and foam filled nylon stock for more strength
• 800m adjustable rear sight
• Round forward assist assembly
• Three-shot burst rather than full auto
• New slip-ring for handguard removal
• Interchangeable handguard
• Spent shell deflector
• Strengthened pistol grip

There are some criticisms of the M16A2 with the biggest being the three round burst setting rather than a fully automatic fire. While the burst setting was designed to help accuracy, it is argued that fully automatic settings are much more desirable in certain settings with a soldier trained in fully auto fire mode. There are also several criticisms of the accuracy of the M855 and M856 ammunition.

Regardless of the criticisms, the majority of opinions on the matter are extremely positive regarding the M16A2 and in November of 1983, the rifle is type-classified as “Standard A.”

Going back to the modified M16A2 that was developed at Picatinny in 1982, the flat-top M16A2 rifle gains quite a bit of traction and is relabeled the M16A2 Enhanced Rifle (M16A2E1) in April of 1984 and is pushed for further development.

In September of 1984, two years after some initial interest in a 5.56mm carbine, Colt holds a meeting to begin development of an M16A2-based carbine, what will later become the XM4. Testing of these prototypes begins immediately as they are made available. In the early months of 1986, the XM4 carbine goes through grueling tests by both the US Marines and Army Special Forces.

Later, in the Spring of 1987, the Marines want to adopt the XM4 as a replacement for pistols in infantry battalions. As it is often the case with these situations, congressional budget approval does not agree with the wants of the military. Funding for this procurement is held back for the next four years. Eventually, the US Army adopts the M4 as well, and the Marines also get their carbine in the early 1990’s. The M4 is essentially the M16A2 with a telescoping buttstock as well as a shortened (14.5″) barrel.

The issue of not having the fully automatic setting on the M16A2 rifles continues to irk a lot of military personnel, and it doesn’t seem like it is going to go away. In 1992, the US Navy SEALs began receiving of the M16A2E3, an M16A2-style rifle with full automatic capability instead of 3 round burst. In the Navy, this rifle is eventually labeled the M16A3, but it is not the same as the commercial M16A3 available from Colt, which is simply an M16A2 with the scope railing.

In 1993 and 94, the M4 and M4A2 Carbine is more abundant in military circles and is officially adopted by the US Army.

In 1995 an executive order signed by President Clinton required all federal agencies to reduce the number of toxic chemicals that are leached into the environment. This is going to require ammunition manufacturers to tweak their product. In 1996, work began on a “green” replacement for the lead core of the M855 Ball cartridge.

Also in 1998, Colt has introduced the M16A4 rifle, which features a removable carrying handle and Picatinny rail for mounting optics and other ancillary devices (Weapons of Modern Marines by Michael Green).

The M4 carbine and the M16A4 will constantly be tested and compared against each other in the following years. One of the main drawbacks of the carbine compared to the M16 rifle is the reduction in reliability mainly due to heating issues of the carbine because of the heat and stress put on the components due to its short length. While initially a problem, these comparisons and numerous tests would lead to improvements to both weapon systems into the 21st century.

The 5.56×45 Modern Era (2000-Present)

There are still changes being made to both the 5.56×45 platform as well as ammunition itself, though not as dramatic of changes as we saw in the early days. What we see a lot of in this period is the continued modification and adoption of several light machine guns and carbines chambered for the 5.56×45 NATO rounds. We also see the US Navy moved to the forefront of advancing the technologies of these rifle systems.

In 2000, a solicitation was made for modifications to the M4 Carbine that will provide measurable and significant improvements in accuracy out to 600m. Some key components of specific areas of interest include but are not limited to: barrels (heavy, fluted, floating), match triggers, magnified optics with range estimation, 5.56 mm ammunition, muzzle devices, bipods, buttstocks and cheek pieces.

In September of 2000, a USMC review board recommends the replacement of the M16A2 with the M4 for all Marine Ground Combat Elements. The ideal components of this platform also include a day optic, assault sling, and a passive night vision device. The Second Marine Division (2d MARDIV) is assigned to conduct the testing of the M4 for possible fielding. During this decade, we see a lot of military branches, and specifically, specialized forces within those branches begin adopting the M4 carbine or other 5.56 chambered carbines.

At the start of 2001, The US Army begins major fielding of the M16A4 along with the M4 and M5 RAS. The latter is an M4 modified with a hand guard designed and produced by Knight’s Armament Company. This system allows a variety of accessories to be attached including vertical grips, tactical lights, and lasers. In US Army field manuals, this weapon also carries the designation of M16A4 MWS (Modular Weapon System) (US Army Field Manual: RIFLE MARKSMANSHIP M16A1, M16A2/3, M16A4 and M4 CARBINE.)

NSWC-Crane (Naval Surface Warfare Center) issues a survey in 2001 to gauge the market for new extended life and high endurance barrels. The point of this is to begin pushing for previously untested technologies including new materials, changes in the manufacturing process, and endurance coatings for the M16 and M4 based weapons, though general improvements for all rifle manufacturing is the end goal. They are hoping to eventually attain a final product that has a barrel life extended to 10,000 rounds but with a goal of 30,000 rounds.

NSWC-Crane continues to probe the market for improvements to the various rifle systems, including the M16A4 and M4 platforms. In 2002, they focused their attention on accessory parts and assemblies such as special purpose receivers (SPR) with improved rail systems. Other accessories for improvement include the magazines, bolt assemblies, barrels, upper and lower receivers, trigger and hammer sets, and well, basically the entire rifle.

In June of 2002, the SPR (Special Purpose Rifle) and its long-range 5.56mm cartridge is approved for use. The SPR is designated the MK 12 Mod 1. This rifle is designed as a semi-automatic marksman rifle. The upper receiver is a mix of military and commercial parts, which is then paired with an M16A1 lower unit. This rifle is still in use by special force units in the modern military.

In the following year (2003), all M4A1 purchased by the Department of Defense now come from the factory with a special heavy barrel installed. If you remember from the previous years, it was shown that the heavier barrels greatly improve performance of the rifle.

In 2004, the HK416, which uses several design ideas from AR-18, is adopted by Delta Force members in replacement of the M4. One of the major reasons for this change is the piston operating system causes fewer malfunctions and improves the lifespan of key parts of the rifle (Matthew Cox. “Newer carbines outperform M4 in dust test”. Army Times. Retrieved 2013-10-18.) A modification of this rifle, the M27 will be key to the story later.

Also in 2006, manufacturers are called on to produce ideas and examples of light Infantry Automatic weapons (IAR). Several weapons are eventually tested rigorously in multiple military facilities and eventually the M27 was picked as the most suitable rifle for the replacement of the M249.
In 2010, the US Army made a change to the 5.56×45 NATO cartridge it used. The M855 standard ball cartridge was replaced with a lead-free M855A1 cartridge which uses a 62-grain projectile, as did its predecessor, but with a copper core, it is lighter than the M855 rounds. The American Rifleman, which is seen to test and critique the pair throughout its history, has a recent article on the new cartridge, Testing The Army’s M855A1 Standard Ball Cartridge.
In 2017, the USMC publicly announced that they planned on providing every Marine in an infantry squad with an M27 rifle, ending a long-standing relationship with the M4.

The 5.56×45 Going Forward

The 5.56×45 NATO has a rich history of innovation, combat use, congressional teeth pulling and a little bit of luck in its long tenure. The rifle platform that chambers the .222 special to the .223 Rem all the way to the multiple variations of the 5.56mm round to today’s currently used ammunition and rifles is an incredible achievement in the firearms world. And while the story shows many shortcomings in the early process, it also shows ingenuity and commitment to excellence.

Modifications continue to be made to the currently equipped 5.56x45mm ammunition, but the question remains if it will be here for the conceivable future? Sure, it will still find itself in civilian circles and given its current deployment, it will remain in military circles for years to come. From the humble beginnings of the AR-15 designed in a small setting to the various platforms today that utilize the 5.56×45 NATO round, it is a testament to the effectiveness of the 5.56×45 NATO.

With that, there continues to be research and design looking into new caliber cartridges and weapon systems. Whether these projects pan out remains to be seen and regardless if the 5.56×45 NATO ever gets phased out or not, the lessons learned from its design, production, and use won’t be forgotten.