The M16 scandal in Vietnam was bad enough that American soldiers were getting killed because of it. Whole platoon were found dead beside their disassembled rifles, clearly trying to make them work in the very last moments of their lives. Some had to use them as bats when the enemy overran them or grab a weapon from the enemy if they could because their own rifles simply stopped firing.

 For years, people tried to cover up what had actually happened to the M16 in Vietnam. When the truth finally surfaced, it turned out to be darker than anyone wanted to admit. So, let’s start from the very beginning. To make sense of why American soldiers in Vietnam ended up hating the M16 so much, let’s first take a look at why this rifle was created in the first place and why it was built the way it was.

 After World War II, the US Army was a mess in terms of small arms. An infantry unit could have several different weapons in several different calibers all at once. There were Browning automatic rifles, M1 Grands, and M1919 machine guns in 306 caliber. Then 45 ACP submachine guns like the Thompson and the M3 Grease gun.

And on top of that, the M1 Carbine in its own 30 carbine caliber. All of this lived inside the same squads and platoon. The war had already shown that supplying frontline units with the right ammunition became a headache. On top of that, you had to produce different weapons, magazines, and spare parts for all of them and then train soldiers to use and maintain this entire zoo of guns.

 So once the dust from World War II settled, the American military wanted to clean that up. The idea was a single do everything service cartridge and a much more standardized family of weapons. Inside the new NATO alliance, there was the same pressure. If another global war broke out, allies wanted to be able to share ammunition to support each other if needed again.

 So this thinking eventually produced 762x 51 NATO, a shortened modernized successor to 3006 that kept similar performance with a smaller case. The Americans then built a new rifle around it that was basically an updated M1 Grand. This became the M14. It had a heavy steel receiver, a wooden stock, a 20 round detachable magazine, and a selector for full auto fire. At least in theory.

 On paper, it ticked the boxes. It shot the new NATO round. It could replace the older grands, carbines and submachine guns, and it looked familiar enough to keep traditionalists happy. In reality, it was a long, heavy rifle weighing around 10 lbs loaded and was extremely difficult to control on full auto with such a powerful cartridge.

 Many armies using similar battle rifles removed the full auto option because it was almost useless without a bipod. At the same time, when they looked at real combat data from World War II, they saw that most firefights happened well inside 300 yd. Beyond that distance, the average infantryman rarely hit anything with his standard rifle, even if the weapon itself was capable of it.

 Submachine guns in pistol calibers were great inside 50 yards, but dropped off quickly after that. Full power 30 caliber rifles were great for long range, but for the typical ranges where most firefights actually happened, they were definitely overkill. Their recoil slowed down accurate rapid fire, and because of the heavier rounds, they could carry less ammo.

 So planners started asking a different question. Whether we really need a big full power cartridge in every rifle, or would a smaller high velocity round that is easier to control and lighter to carry actually be better for most soldiers. In the background, there were American research programs like Project Salvo that were looking at hit probability instead of just raw power.

This was the situation Eugene Stoner walked into at Armalite. While the army was officially trying to modernize the M14, Stoner went in another direction and designed the AR10. It still used 762x 51, but instead of a heavy steel and wood construction, he used aircraft grade aluminum for the receiver and synthetic furniture to save weight.

 He also used a new gas system that tapped propellant gas from the barrel and routed it back into the bolt carrier, where the bolt and carrier worked like an internal piston. This allowed a straight line layout between the barrel and the stock and helped keep recoil more manageable. But the really important shift came when they started paying attention to the small caliber high velocity idea.

 There were new experimental small ball cartridges like the 223 Remington which would later evolve into 5.56 NATO. They fired a much lighter bullet at very high speed. The thinking was that if you drive a small bullet fast enough, you still get serious damage on the human body, yet the recoil stays low and each cartridge weighs much less.

 That means the same soldier can carry far more ammunition and he can fire more controllable bursts, which again feeds into that hit probability idea. Stoner took the general layout and operating system of the AR10 and basically scaled it down around this new small caliber. The result was the AR-15. Now, you had a very modern looking rifle with aluminum receivers and plastic furniture that weighed under 7 pounds and was very easy to handle.

 With the long 20-in barrel, the light 556 bullet left the muzzle at roughly 3,200 ft per second. At those speeds, and when the bullet hit bone or dense tissue, it could yaw, fragment, and produce nasty wounds that were not far off what the larger 762 could do, at least on paper. We’ll see how that worked in practice in a bit.

 The first big difference was that in semi-automatic fire, the AR-15 had almost no noticeable recoil compared to the M14. In full auto, it was actually controllable, so a soldier could keep bursts on target instead of spraying bullets all over the place. So once the design went through trials and development, it evolved into the standardized military version, the M16.

On paper, the US military finally had what it wanted, a light rifle that was ideal for engagements under 300 yd and a single standard weapon that could gradually replace the older guns. Compared to 762, individual 5.56 cartridges were much lighter, so an infantryman could carry roughly three times as many rounds for the same weight.

 As a general issue rifle, the M14 ended up with the shortest career in US history and was pushed aside by the newly developed M16, which promised a bright future for the American Army. Spoiler alert, before that, it would cost many soldiers using it their lives. And you’re now going to see why. The real reason so many of them came to hate the M16 was not the basic idea of a light small caliber rifle at all.

 It was something much uglier in how the rifle was pushed into war and what was done or not done to make it reliable when their lives depended on it. So, let’s explain. When tensions in Vietnam began to rise, the first M16s were still in their experimental phase, and they were quietly sent out for combat testing. They went to American advisers and elite South Vietnamese units who were already fighting Vietkong guerrillas.

 In those early trials, the rifle looked like a complete success. Soldiers liked how it handled its lightweight on long jungle patrols and how easy it was to shoot accurately. Reports from those units described the new rifle as superior in almost every way to the heavy World War II era weapons they had been using.

 The plastic stock and aluminum receivers did not swell in the tropical humidity the way the wood on the M14 did. Most importantly, soldiers using M16s in these trials reported very few malfunctions, even after thousands of rounds in training and combat, which only reinforced the idea back in Washington that this was the answer the army had been looking for.

 On the strength of these glowing field reports, the decision was made to adopt the rifle. The army ordered tens of thousands of AR-15based rifles. By the mid 1960s, the weapon was fully committed to production and was being issued in large numbers just as the ground war in Vietnam escalated in 1965 and American infantry units started arriving in force.

 So, picture what happened next. Tens of thousands of young soldiers stepped off transports in Southeast Asia carrying sleek black rifles everyone had told them were the most modern weapons on Earth. They had every reason to believe they were holding a cuttingedge rifle that would give them a clear advantage over gorillas armed with what they saw as old worn AKS and World War II era weapons.

Patrols went out into the jungle scrub and rice patties. And not long after, the first big firefights broke out. That was when the shock hit. After only a few magazines in real combat, some of the new M16s simply stopped working. The gun fired, then suddenly failed to cycle or refused to extract the spent case, completely jamming the gun.

 Soldiers grabbed rifles from fallen comrades and kept shooting until those rifles seized up as well. Men tried to clear jams under fire, pulling charging handles and disassembling rifles in the mud to try to find the problem. But in many cases, there was nothing they could do to get them running again.

 Reports began to pile up of whole squads and platoon where a frightening percentage of rifles failed during contact. Investigators and later congressional hearings described dead Americans found beside their disassembled rifles or with cleaning rods driven into the barrel obviously killed while they were still trying to clear a stoppage.

 There are accounts of units where roughly a third of the rifles malfunctioned in a single engagement and the fight degenerated into brutal close combat with soldiers resorting to bayonets, rifle butts, pistols, grenades, and whatever else they could lay their hands on. In that situation, anyone who still had a working sidearm, a shotgun, or even an enemy AK was considered lucky.

 As trust in the weapon collapsed, men started carrying more hand grenades and did whatever they could to get spare pistols or older weapons. The M16 was meant to replace. No one seemed to have any idea why this was happening. They had been told they were carrying the finest rifle in the world.

 It had proved great in testing, yet in the middle of Vietnam, it would just stop firing after a couple of magazines. Okay, so what was actually happening and why? First, everything was made worse by a decision that now looks insane in hindsight. The M16 had been advertised and sold within the bureaucracy as a self-cleaning rifle.

 Colt’s promotional material and some early army messaging pushed the idea that the new materials and the gas system meant much less maintenance. As a result, the first large batches of rifles were sent into a dirty, wet jungle war with completely inadequate support. units received no proper 22 caliber cleaning kits for their weapons.

 Some troops ended up improvising, trying to clean rifles with aircraft fuel or whatever they could find. Soldiers were asking their families in letters to buy civilian cleaning rods, brushes, and gun oil and mail them to the front. There is even a documented case of a soldier who was the only man in his platoon with a cleaning rod.

 During a firefight, he ran from position to position trying to clear out stuck cases and get other men’s rifles back into action until he was killed. Stories like that spread quickly and hardened the feeling that something was deeply wrong with this weapon and with the people who had sent it into combat like that.

 One of the biggest causes of the jams was a particular type of stoppage called a failure to extract. The spent cartridge case would expand in the chamber and stick there. The extractor claw on the bolt would rip through the rim instead of pulling the case out, leaving it firmly wedged in place. The only way to clear that kind of jam in the field was to hammer a rod down the muzzle and punch the empty case out from the front.

 And those rods were exactly what many of the early units did not have. Chambers that were not chrome lined also corroded and pitted quickly, which made stuck cases even more likely no matter how much a soldier tried to clean his rifle. Also, for reasons that were still unknown at this point, the M16 fouled quite a bit and got very dirty inside after just a couple of magazines, while the rate of fire was varying and much less controllable than what had been depicted in testing.

 When Colton Army investigators looked into the problem, and when journalists and Congress began to dig as well, they eventually uncovered the very dark truth. During early development, the AR-15 had been tested with an extruded stick powder made by Dupont called IMR4475. It burned at a predictable rate, produced the right pressure levels the rifle was optimized for, and left relatively little fouling in the gas system.

 This powder was used in ammunition fired during testing and the M16’s experimental stage, and the rifle had run well with it. But in 1964, just as the rifle was being pushed into mass production, the Army Ordinance Department quietly changed a key part of the equation. Because of cost and logistics reasons, criminal negligence, or even outright deliberate sabotage, they switched the standard propellant in the 5.

56 cartridge to a ball powder called WC846. Ball powder was cheaper to make in huge quantities and the army already had large stockpiles because it had been used for artillery and ammunition produced during World War II. Basically, the idea was that if we already have piles of this powder, let’s use it instead of the more expensive one. However, the problem was that this ball powder behaved very differently.

 It raised gasport pressure, drove the cyclic rate much higher, and produced heavier fouling in the chamber and gas system. To make matters worse, this change was approved with little or no realistic compatibility testing in the actual M16. Eugene Stoner himself was not even consulted about the switch, and no one stopped the process to retune the rifle for this new ammunition.

 With the new ammo, the promising new rifle was now being handed to tens of thousands of infantrymen about to go to Vietnam and use it in real combat. So when those young Americans marched into the jungle believing they had the most advanced rifle in the world, what they actually had was a weapon whose ammunition had been altered at the last moment to use a dirty, hotter burning powder that completely messed up a rifle that had been fine-tuned around a different powder that pushed the bolt carrier back faster and raised the cyclic rate well

above what Stoner had set the system up for. Because of the higher pressures, it also caused that signature quirk of tearing the rim off the cartridge and leaving it stuck in the chamber. Carbon and unburned granules were blown into the gas tube and bolt carrier and then baked in place, building up a thick, gritty layer in the moving parts in a hot jungle with unlined chambers that rusted and pitted.

 And with soldiers given no proper cleaning gear, that fouling turned the so-called self-cleaning rifle into something that could get its operator killed in a firefight. And that is exactly what was happening. Army Ordinance did not stop there. They also insisted on adding a forward assist to the standard Army version.

 Stoner and the Air Force both argued that it was unnecessary. His design already allowed the shooter to pull back and release the charging handle if a round did not chamber, which either fixed the problem or ejected the bad round. Ordinance wanted a manual way to pound the bolt into battery, similar to what they were used to on older rifles.

 In theory, it let a soldier thumb the bolt all the way forward if it was slightly out of battery. In practice, if the problem was a swollen case or a filthy chamber, ramming the bolt by force could only make things worse. If all this was not enough, there were also problems with early magazines. The standard 20 round magazines were cheaply made and intended to be semi-disposable.

 In other words, you use them once or twice and discarded them. But they overdid this. So their feed lips bent easily and the springs were weak, which caused rounds to jam inside and not feed properly. Many Vietnam veterans remember loading a maximum of 18 rounds into a 20 round magazine to ease pressure on the spring and tapping the magazine on a helmet to free any cartridges that might be stuck inside.

You saw that in movies, surely. And it is not some cool Hollywood trick, but what soldiers actually did. Can you even imagine going into combat knowing how sensitive your weapon is and how many things could stop it working just when you need it the most? By the mid 1960s, the jamming crisis could not be ignored anymore.

 Letters from Vietnam and press stories about Marines dying because of jammed M16 rifles reached the American public. Congressional hearings followed and the army’s own review panels had to admit what had gone wrong. Before anyone argued about blame, there was a more immediate problem. They had to stop American soldiers from being killed.

 The first fix was that proper cleaning kits and lubricants were now rushed to frontline units. New production rifles got a small storage compartment in the buttstock with a trapoor so every soldier could carry a basic cleaning kit directly in the weapon and strict cleaning discipline was enforced. One of the most important upgrades was chroing the chamber and then the entire bore to resist corrosion and make stuck cases less likely.

 A revised buffer and spring along with adjustments to the gas port brought the cyclic rate back down into the intended range and reduced stress on internal parts. The original open threeprong flash hider which tended to snag on vegetation and let debris into the muzzle was replaced with a closed bird cage design.

 The powder problem was addressed too. The ammunition was reformulated so that the 5.56 round still hit the required velocity, but produced less fouling and a more manageable gas curve in the rifle. Over time, new ball powders replaced the earlier ones, specifically to cut down on carbon buildup and stabilized performance.

 Better magazines appeared as well, first improved 20 rounders and then more reliable 25 and 30 round designs, which gradually fixed the feeding issues that had haunted the system in its early years. Later trials of the M16 used ammunition loaded with the original type of powder, and the catastrophic level of failures seen in Vietnam simply did not show up.

 With all of those changes in place, the M16A1 in Vietnam became a very different rifle from the one that had betrayed so many soldiers in the mid 1960s. Reliability in the field improved drastically, and new troops coming into the war later often had no idea how badly the first generation had suffered.

 For them, the rifle was simply the standard issue weapon, light, accurate, and working just as intended when it was looked after properly. But not before so many men had to die first. Whether this was just a tragic chain of bureaucracy and bad decisions or something closer to sabotage from within their own system is still a question to this day.

 The congressional investigations pointed to serious negligence and corruption. Although in the end, no officer or official was criminally charged for it. No one was fired, demoted, or prosecuted specifically for the M16 disaster, even though everyone understood that frontline troops had paid for those mistakes in blood.

 As for the rifle, once the problems were finally solved, it went on to become one of the longest serving designs in American history. It gradually shifted toward the M4 carbine, a direct descendant of the original M16, just more compact and modular.