Green Jungle, Black Rifle; The M16 in Vietnam

Green Jungle, Black Rifle; The M16 in Vietnam

It is public knowledge that the tropical jungles of Vietnam turned the M16 from space-age assault rifle to unreliable junk which got good men killed. The specter of dead servicemen clutching jammed rifles looms large in the cultural consciousness. It is certainly true that the rifle’s issues in Vietnam are taken to hyperbole, even to the extent that they are thought to affect the M16/M4 family almost 50 years later. Seeking to address these deficits, it is beneficial for us to address each issue which plagued the rifle in turn, and its corresponding solution. In so doing, we shall both see that each issue has been resolved in turn, and understand the underlying factors of procurement irrespective of the AR-15 itself which led to its failures.

The genesis of the AR-15 came from the combination of two strands of innovation, that of a Small Caliber, High Velocity rifle, and the weight-savings of Armalite’s use of aluminum. Beginning with the 1952 Hall report, the SCHV concept shunned the American military’s commitment to the long-range performance of rifle ammunition, arguing that the majority of effective infantry fire took place within close range. The concept consisted largely of a series of experiments, including tests of modified .220 Swift and M1/M2 Carbines in a high velocity .22 cartridge, as the US remained wedded to the full power .30-06 and 7.62×51 cartridges. Testing continued under Project SALVO, but it would remain until the introduction of the AR-10 for the SCHV concept to take flight.

Credit to James D. Julia Auction House


Incorporated as a division of Fairchild Engine and Airplane Corporation, Armalite was founded in order to take advantage of the aircraft industry’s advances in design materials, namely aluminum and fiberglass. Armalite’s relationship with the US Military began with the AR-5, a lightweight aluminum survival rifle adopted by the Air Force as the MA-1, but it was Eugene Stoner’s AR-10 design which would leave a greater legacy. Entering the tumultuous competition to replace the M1 Garand in 1956, the AR-10 consisted of of a multi-lug rotating bolt, aluminum receivers, and fiberglass furniture. Armalite’s penchant for light, innovative rifles was in full display, as the rifle weighed a pound and a half less than its lightest competitor, the M14. This innovation was perhaps the undoing of the program, as its steel and aluminum barrel burst during testing, and a subsequent series of acquisition programs went against the AR-10.

As the prospects of the 7.62 NATO AR-10 came to an end, the nascent SCHV emerged again. Two prior test cartridges in .22 caliber, a 68gr homologue of .30 M1 Ball and a 41gr offshoot of .30 Carbine, were decided to be too big and too small, respectively, and in 1955 the 55gr predecessor to 5.56 was proposed to the Chief of Ordnance. Work quickly proceeded under Robert Fremont and James Sullivan to scale down the AR-10 to the interim .222 Remington cartridge. In 1959, five days after the M14 was adopted, the Continental Army Command placed a request for ten of these new rifles for an Infantry Board trial. The AR-15 was born.


The AR-15’s involvement with the US military parallels that of the US military’s involvement with Vietnam. Undergoing combat testing as part of Project AGILE in 1962, the rifle produced excellent results in comparison with the older M2 Carbine. So good were the test results that an order of 8,500 rifles for the US Air Force was approved on May 15, 1962, with a further 19,000 the next year alongside a small Navy order intended for SEAL use. Gradually, beginning with elite units and advisors, both Americans and AR-15s began to filter into Vietnam.

Though elements of the Army firmly cleaved to the recently adopted M14, the earth-shattering Hitch report which suggested that the AR-15, AK-47, and even the M1 were all superior spurned the Army to consider the adoption of the AR-15 at length. Concurrently with this controversial process, the SPIW program to produce a revolutionary infantry weapon was seen to be imminently successful, and production of the M14 was cancelled in January 1963. As an interim to the SPIW, and with M14s no longer being produced, the famous “one-time buy” of 85,000 AR-15s by the Army was made in March 1963. With the classification of the Air Force rifles as M16, and the forward-assist modified Army and Marine rifles as XM16E1, the era of the M16 had arrived.


Its coming was not to be a placid one. Initial reactions by combat troops were exceedingly positive, but in August of 1965 the Project Manager Rifles (PMR) began receiving reports that XM16E1 was encountering “freezing” of the bolt and bolt carrier. With the issue of XM16E1 rifles to all US Army maneuver units in Vietnam by late fall of ‘66, these reports increased in severity, to the point where the PMR was receiving letters complaining of excessive stoppages and malfunctions from Battalion COs. According to the independent Crossman report after the fact, 50% of surveyed Marines and Soldiers had encountered serious malfunctions with the XM16E1s, 90% of which were failures to extract. So bad was the rifle’s reputation for reliability that, even with its other superlative characteristics, almost half of those questioned said they would prefer the M14.

The issue which is commonly perceived to have most damaged the M16’s reliability was not with the M16 itself. Initially the 55gr 5.56 round intended for use by the M16 family, the M193 round, was loaded with IMR4475 powder and held to strict velocity and chamber pressure requirements. The approved ammunition producers, Remington, Winchester, and Federal, all held the requirements to be unachievable when limited to IMR4475. It was at this point that Olin introduced a fateful new powder, WC846 ball powder, which was approved as a substitute in April of 1964. Crucially, this was approved without any compatibility testing in real M16 rifles. Testing of M16s was conducted using the original IMR4475, while rifles in the field would be using WC846. Almost accidentally, it was discovered that the new ball powder increased the gas port pressure, and thereby the cyclic rate. This change in the pressure curve, essentially meaning that the rifle attempted to extract the case much more violently, led to a dramatic uptick in failures to extract.


In the end, the solution to the problem of higher cyclic rates came from an earlier issue, that of light primer strikes. In the original AR-15 design, the bolt moves under the influence of an recoil spring and recoil spring guide, which lacks any buffering effect. With this design, however, the rifle is vulnerable to bolt bounce and attendant light primer strikes. To resolve this, the action spring guide was replaced with a buffer. Adopted in December 1966, this new design not only fixed the issue of bolt bounce, but coincidentally lowered the cyclic rate, even when using faster WC846 ball powder. The Army seized upon this, and initiated a refit program to replace all recoil spring guides with buffers. Completed by late fall of 1967, the buffer refit program reduced the rate of malfunction, even with WC846, to half of that of rifles with recoil spring guides. (.25/1000 vs .49/1000). 1968 testing in Panama found M16A1 rifles with buffers using ball powder to be more reliable than those using original IMR powder. Though ball powder has a deservedly poor reputation for being an untested change to a combat rifle, its issues were definitively solved with the buffer refit program.

As earlier described, the vast majority of the malfunctions experienced by the M16 family were failures to extract. These failures are typically caused by either deficiencies in the case hardness, or excess friction acting upon the case due to fouling or corrosion of the chamber, that is, the segment of the barrel which supports the cartridge case. The problem of corrosion in particular is exacerbated by hot, humid environments such as tropical jungles. Vietnam was, of course, not the first time US small arms had fought in the jungle, and the Ordnance Corps had set forth in 1957 a requirement drawing from WW2 experience that all small arms have a chrome plated bore and chamber. This chrome plating would provide resistance to the effects of corrosion even in the absence of regular cleaning, thereby alleviating issues of failure to extract. Though the technology did not exist to produce .22 caliber chrome lined barrels at the outset of the M16 program, Springfield Armory recommended that efforts to this end begin immediately. To the detriment of the rifle, this suggestion was ignored, and it was not until May of 1967 that a chrome-plated chamber was approved. In addition to new production M16 rifles having chrome lining of the chambers and eventually the entire barrel, in-service rifles were often rebuilt with chrome lined barrels to alleviate corrosion issues in older rifles. In tropical testing in Panama, M16A1s with chrome chambers performed far better than their unlined counterparts.


Yet another issue regarding the chamber, born from failures in training and excesses in marketing, was that of weapon maintenance. Fouled chambers will become corroded chambers in the absence of adequate cleaning, especially when fighting in tropical environs with rifles bereft of chrome lining. Colt had, however, advertised the rifle as “self-cleaning”, meaning cleaning kits were not created, much less issued. The Ichord commission found a complete absence of the materials or training to maintain the weapons, reporting that “many [Soldiers] said they were never taught the maintenance of this rifle… Some you could not see daylight through the barrel. The barrels were rusted, and the chambers were rusty and pitted.” In response, cleaning kits were hurriedly devised and issued, along with a program to reinstate the vital skills of weapons maintenance. This effort included the now famous comic book series explaining the cleaning procedures of the M16 rifle.


Most crucial amongst this effort was the chamber brush. Beginning in January ‘67, these tools were urgently brought into Vietnam. Necessary for the Soldier to clean the chamber and locking lugs, these tools helped prevent corrosion and fouling around the chamber, reducing the occurrence of jamming.Tellingly, when a USAWECOM survey team visited Vietnam in 1966, they reported that the majority of M16 rifles were poorly maintained, “with the exception of the weapons of the 1st Brigade, 101st Airborne Division, the 173d Airborne Brigade, and the 5th Special Forces”, units noted for having prior training in maintenance and care of the M16 rifle.

A common misconception is that the M16A1 alteration, particularly the addition of the forward assist, played a role in resolving the rifle’s issues. This is flawed for two reasons. Firstly, the Army insisted, to the consternation of the other branches, on a forward assist device from the outset. This position was set down by October ‘63, 3 years before mass-issue of XM16E1 and large-scale issues of reliability being reported. Secondly, the issues in Vietnam largely pertained to the extraction of fired casings, a malfunction which the forward assist was useless to resolve. The Air Force, the first branch to adopt the AR-15 in large numbers, was so insistent that the forward assist was useless cost and complexity, flatly refused to purchase rifles with the device, leading to the Army and the Air Force using separate variants of the M16.


Taken individually, none of these issues would have caused the failures the M16 experienced in Vietnam. A properly cleaned rifle shooting ammunition it was designed to use will function reliably even without a chrome lined chamber. A fully matured and maintained rifle will be able to handle multiple types of ammunition, including dirtier powder types. With proper ammo, a well built rifle can fire thousands of rounds without cleaning. The failure of the Project Manager Rifles in particular, and of the M16 acquisition process as a whole, go beyond that of any one issue.

At the most basic level, a prototype rifle which had not had significant design work done since 1958 was considered by the Army to be a finished product in 1963. This, combined with the “one-time buy” attitude, precluded testing and development of the rifle as a system, and meant that problems were only given the barest minimum treatment in order to avoid schedule slippage. Changes were made to the ammunition without any testing in the rifles, leading to troops in the field being given untested combinations. Troop maintenance training and support for the rifles was sorely lacking, and requirements such as a chrome lined chamber were overlooked. Though the process was considered by many in Congress to be criminally negligent, the end result with the finalization of the Technical Data Package in 1968 was a rifle that reported a field malfunction rate consistently below 1 per 1,000 rounds.







  1. Maybe worst combat rifle ever to be mass produced. With its defects and flaws in its design. And with all internal parts designed to tight, the nightmare began at once. Hypersensitive to weather, shock and in sporadic incidents of sea water exposures [Marines] the weapon has been reported to explode.


    • Buddy Burke, while your criticisms are certainly valid for the earliest models of the AR-15, which were honestly prototypes, the rifle as is fielded functions from the sands of Iraq to the cold of Alaska, so the phrase “hypersensitive to weather” strikes me as odd. I’d be curious to see a citation for M16s exploding when exposed to sea water.


  2. Factual errors abound. Writer needed to avail himself of the extensive report written by Col, Harrison and published in two parts in the American Rifleman before putting pen to paper.


    • Old Persimmon, would you mind sharing specific factual errors? Unfortunately I’ve not read anything published in the American Rifleman written by the good Colonel, as my NRA membership is rather recent. If you’ve a link to a copy I’d love to read it.


  3. There was one amusing incident where Winchester cut the wash time after the acid bath but maintained the shelf life by adding more calcium carbonate (powdered limestone). It was a little dirtier but worked in the 7.62 and .50 caliber rounds. In the 5.56, it would form lumps of partially burned powder, limestone and jacket material. You could remove it from the bore with J-B Bore Cleaner but it played hob with the AR gas system. The ammunition was recalled and the bad powder sold off as H380. It did the same in bolt action rifles as well. Had an awful time cleaning it out of my .222 Magnum.


  4. A user on another site, FreeRepublic, going by the name “schurmann” posted an interesting comment which I’d like to briefly address, since I can’t comment directly on their forum.

    “Missing from the AAR article is any mention of the dessicant-residue issue. This was covered extensively in American Rifleman Magazine, in the late 1980s if memory serves. At one point calcium carbonate was used by Olin in the manufacture of WC846, to neutralize acid solvents and hasten product drying. No problems had arisen with calcium carbonate in propellants for other rounds, but it proved to increase clogging of the M16’s gas tube.” 4/22/2017, 11:00:39 PM

    To be entirely honest, I must’ve skipped over the calcium carbonate section of the book I was going over, I do apologize for the omission, and appreciate the correction. As related to an earlier user, the late 80s was before my time, so if you’ve a link to the American Rifleman article I’d much appreciate it. “The Black Rifle” by Stevens seems to imply that the CaCO3 issue was limited to a specific lot of WC846, and testing from 67-69 at Frankford showed production lots rarely approaching the max 1.0% CaCO3 content. The allowable calcium carbonate content was reduced to .25% in Sept 69, so any presence of calcium carbonate isn’t necessarily an awful thing, and its my understanding that no definite link between the rifle’s failures and CaCO3 was proven.


    • Hi Millett,

      There’s a lot more to the CaCO3 issue than the Army and Winchester will ever admit. Much of what I know comes from personal experience and a casual friendship with one of Winchester’s ballistic engineers, Herman Bockstrup. There were s9me articles in the 1970s about the issue.

      Actually, Winchester has a lot of skeletons in their closet. Did you know they were selling 8mm Mauser ammo to Nazi Germany until the day Germany invaded Poland? I kept a single cartridge as a souvenir.



      • If you would be so kind as to talk with Mr. Bockstrup with regards to the CaCO3 issue and publish that somewhere on the internet, I would be extremely grateful, as I’m sure would posterity. Especially since the 70s was long before many of our times, and finding articles from that period can be quite difficult.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s