From M16 to M16A1
From M16 to M16A1
M16
M16A1Caliber: 5.56×45mm M193
On February 8, 1964, the United States Air Force officially designated the XM16 as the "United States Rifle, Caliber 5.56mm, M16". Due to the AR-15's charging handle only having the function of pulling the bolt carrier group back, without assisting in chambering a round, and the bolt carrier group being relatively lightweight, if for any reason the bolt carrier group fails to fully close, the bolt will not lock, leading to concerns about this issue. Therefore, the experimental version adopted by the Army added a bolt assist device (bolt assist handle, also known as the "forward assist") to the M16, and it was designated as the XM16E1. Thus, the main difference between the XM16E1 and the M16 is whether there is a piston-shaped bolt assist handle on the right side of the receiver. In addition, the surface of the M16 receiver is smooth, while the XM16E1 receiver has multiple serrations on the right side to accommodate the bolt assist handle. If the bolt fails to fully close, the user can manually push the bolt forward using this bolt assist handle.
Actually, at that time, Colt, the Air Force, the Marines, and Eugene Stoner all believed that there was no need to add this complex device to the rifle, which would increase the procurement cost by $4.5, and they also believed that this device had no practical benefits. (QBQER or C2KER are familiar with this device. Mr. Ding, he has fired countless rounds with his Bushmaster M4 without ever using this device. Of course, the shooting range environment is much cleaner than the military environment, and civilians may maintain their beloved firearms more diligently than soldiers maintain government property, but I couldn't find relevant survey information on the actual usage frequency of this device.)
Regardless of whether this controversial "bolt assist" device is effective, the Army still ordered 840,000 XM16E1 rifles with this device on February 28, 1967 (some sources indicate that Colt won this contract worth about $91.7 million on June 16, 1966), and officially designated it as the "United States Rifle, Caliber 5.56mm, M16A1" (some sources say the M16A1 was officially designated on February 23, 1967). However, during the period from 1965 to 1967, the XM16E1 exposed many problems in combat in Vietnam.
AR-15（Colt Model601）
AR-15（Colt Model602）
Army M16A1 (Colt Model 603 late model)
Air Force M16 (Model 604)
Model 601 in the museum
The right side of the 601 receiver is a special name for the flat lower receiver of the early AR-15, which is called "Slabside".
The right side of the lower receiver of the 602 model is still a "flat" receiver
The 603 model began to add an auxiliary push handle on the right side of the upper receiver during the XM16E1 period, and a convex rib was added to the lower receiver near the ejection port. This type of lower receiver has a special name called "Partial Fence"
When the 603 model was officially designated as the M16A1, a rib was added around the magazine release button to prevent accidental operation. This type of lower receiver is also nicknamed "Full Fence".jpg)
The Air Force's M16 (Type 604) has two types of lower receivers, the early "half-fenced" and the later "full-fenced"
The Air Force's M16 (Type 604) has two types of lower receivers, the early "half-fenced" and the later "full-fenced"
An early model XM16E1 equipped with a 3X20 scopeRegarding the transformation of the AR-15 into the M16, previous problems in the early stages of the Vietnam War were frequent, and both the M14 and SPIW can be said to have "indelible achievements". The story starts in the 1950s. When NATO was implementing "standardization of ammunition", that is, unifying calibers within NATO, the United States believed that the T65 7.62×51mm cartridge had a long range and strong penetration, and strongly opposed any reduction in the power of small-caliber ammunition. The United States, with its dominant position, exerted strong influence, leading NATO to officially decide on the T65 cartridge as the NATO standard cartridge in 1953, and the U.S. military selected the Springfield T44 as the standard rifle, which was standardized as the M14.
The M16 did not replace the M14 overnight. This 1965 image of the US Army during the Vietnam War shows that the M14 is still in widespread use.
The M14 was just put into service when it was immediately deployed to the Vietnam battlefield. In the jungle and mountainous areas of Vietnam, the shortcomings of the M14 were evident. The M14 was 1120mm long and weighed 4.54kg when loaded with a full magazine. Due to the large caliber of the 7.62mm ammunition, the recoil was very strong when firing fully automatic, making it difficult for the shooter to control, and the shooting accuracy was poor. The most unbearable thing was that the M14s issued on the Vietnam battlefield were all equipped with a selector lock (see the specific description in M14/M14A1), so soldiers could only fire in semi-automatic mode. Under the strong firepower of the AK47, American soldiers using the M14 suffered greatly. In addition, because both the rifle and ammunition were too heavy, the amount of ammunition carried by individual soldiers during patrol missions usually did not exceed 100 rounds. In addition, the M14 had too many wooden components, so in the humid jungle of Vietnam, it would quickly absorb too much water, leading to deformation, loosening, and even rot, seriously affecting shooting accuracy.
The backward thinking of the senior U.S. Army officials led to the birth of the M14, a weapon that was outdated for its time. However, the painful experience of the senior Army officials placed their hopes on another weapon that was ahead of its time—SPIW (even in 2020, some of the paper-based data relies on the times, which is too science fiction). The senior Army officials regarded the M16 as a transitional weapon between the M14 and SPIW, so they did not pay much attention to the development and testing of the M16. As a result, it was the failure of
SPIW that led to the formal adoption of the M16; but it was also because SPIW failed too quickly that the M16 did not have the opportunity to undergo more thorough testing and improvement before being put into service, and because of the senior Army officials' attitude towards the M16, the early reliability of the M16 was questioned.
The XM16E1 made its first appearance in combat in the Ia Drang Valley battle in November 1965 and performed quite well. Colonel Harold G. Moore, later promoted to Major General, wrote in a report: "This victory was brought by brave soldiers and the M16." (Sidebar: Harold Moore and Joseph L. Galloway, a war correspondent at the time, co-wrote a memoir about the Battle of Ia Drang, titled "We Were Soldiers Once... and Young," which was adapted into a film of the same name starring Mel Gibson in 2002.)
Photo of American soldiers using XM16E1 in the battle of the Drang River Valley in Vietnam in November 1965, taken by Galloway. This photo also served as the cover of "We Were Young Soldiers"But as the number of XM16E1s issued gradually increased, their reputation also gradually worsened. Starting in the fall of 1966, reports of M16 failures began to emerge on the Vietnam battlefield, and many reports of combat losses mentioned problems with the rifle. In May 1967, a Marine wrote in a letter:
"I just received your letter as I was boarding the ship today. We've been on an operation since the 21st of last month. Currently, the enemy has suffered heavy casualties, and the Marine casualties are relatively minor, so I was able to come back to base to read the newspapers. Let me give you some statistics to show why the casualties are relatively minor. In our battalion, nearly 1,400 men were lost, and about half of them were able to return. We lost 250 people in the company, and 107 people returned. We lost 72 people in the platoon, and 19 people returned. I think my luck has run out, and they (the reaper) will eventually come for me. But I was only hit by a small piece of shrapnel. I hope my buddies can say the same.
... Believe it or not, do you know what killed most of us? It's our own rifles. Before we left Okinawa, we were all issued this new type of rifle—the M16. In fact, we found that almost everyone died while repairing their rifles—because their rifles malfunctioned. A female journalist who was with us took these photos, but when the Pentagon found out, they wouldn't let her publish them. They said they didn't want to affect public sentiment in the United States. Isn't that ridiculous?"
Colt immediately dispatched several expert teams to the scene, and the United States Senate Armed Services Committee, American Rifleman magazine, and others also sent people to investigate and interview. At that time, the main problems with the M16 were: severe chamber fouling, jamming, cartridge breakage, magazine damage, barrel and chamber rust, lack of cleaning tools, especially in adverse conditions, the situation was even worse. At this time, the photos taken by Catherine Leroy were published in the Paris Match magazine, and the news spread to the country, causing a sensation, and the wave of criticism against the M16 continued to rise, especially with the push from those who opposed the adoption of small-caliber ammunition.
The causes of these failures were multifaceted. Vietnam's climate is humid and hot, and if not cleaned and maintained properly, the rifle can easily rust, but switching to rifle ammunition was the main reason. The M16 originally used IMR4475 single-base cylindrical propellant produced by DuPont, which had a fast burning rate, a quick pressure curve rise, and little residue. However, shortly after, DuPont informed the Army that they could not mass-produce IMR4475. In January 1964, the Army decided to adopt the WC846 double-base spherical propellant from Olin Corporation, believing that this propellant was easy to produce, cost-effective, and had a slow burning rate, reducing peak pressure, which was conducive to increasing barrel life, and the original T65 cartridge also used this propellant. However, things did not go as planned. Many problems arose after the M193 cartridge adopted the WC846 propellant: spherical propellant residue would leave some sticky residue in the M16's barrel and gas tube after burning, and because the barrel was not chrome-lined, and the gas system lacked appropriate maintenance equipment and suitable lubricants, it was difficult to quickly restore the rifle to normal use; the ballistic characteristics of the spherical propellant led to pressure in the gas ports, coupled with the light weight of the buffer, the M16's fully automatic rate of fire increased significantly from 750-850 rounds per minute to 850-1000 rounds per minute; in addition, due to the high residual chamber pressure when the bolt unlocks, the residue also increased the friction between the chamber wall and the cartridge case, resulting in frequent jamming and case rupture phenomena; furthermore, the lack of an effective management system for the entire production process of the M16 was also a significant reason for the quality problems.
Stoner himself always had regrets about switching to a different propellant, and it is said that he had a conversation with Congressman Frank Weyher. At the time, Stoner was reviewing the technical data for the M16 rifle after the propellant change:
Weyher: What's your opinion?
Stoner: I suggest it's better not to change.
Weyher: The Army has already decided to do so.
Stoner: Since the decision has already been made, why ask for opinions?
Weyher: I thought I'd feel better if you agreed.
Stoner: Well, then let's both be uncomfortable!
Additionally, in the early manuals printed by Colt for the CAR-15 rifle family, the theoretical rate of fire for the XM16E1 was listed as 750 rounds per minute, but later data often mentions theoretical rates of fire of 900 rounds per minute for the M16 and M16A1. This is also related to the change in propellant.
In addition to the reasons mentioned above, the lack of necessary training, guidance, and maintenance equipment for the troops equipped with the M16 also led to many dramatic failures of the rifle in combat. One of the advantages of the Stoner system is the "piston" formed by the bolt carrier and receiver moving on the barrel axis, which minimizes changes in the center of mass of the bolt carrier during movement, thereby not adversely affecting accuracy, and the lack of an independent piston also simplifies the structure and reduces moving parts. However, the disadvantage of this system is that gunpowder gas enters the bolt carrier directly, easily causing carbon buildup in the bolt carrier, so the M16 needs to be regularly cleaned and lubricated to ensure its reliable operation. What made things worse was that the military was told that this space-age weapon did not need cleaning, so no appropriate maintenance equipment was provided. If the original IMR propellant had still been used, this might have been true, but unfortunately, the current "dirty" spherical propellant was used. As a result, the M16 frequently jammed on the battlefield.
But regardless of the reasons, the debate over the M16 has once again erupted, with Stoner's latest design, the Stoner 63 weapons family, sent to Vietnam for testing, and the SPIW steel spear test weapon program restarted. Fortunately, this time, the treatment of the M16's problems was much calmer than that of the M14. A congressional committee began investigating the problems with the M16 on May 15, 1967, with the chief representative being Richard Ichord, a Democratic member of Congress from Missouri. He conducted tests on the M16 failures at Benning and Pendleton camps and directly went to Vietnam to assess the issues. The investigating committee submitted a report in late June 1967 stating that "the so-called heavily problematic M16 actually is an excellent rifle, and the various problems discovered in its application are due to poor internal management within the troops."
However, difficulties in extracting shells and the issue of firing rate are caused by design flaws. To address some of these design issues, the calcium carbonate content in the M193 cartridge, which easily produces residue, was reduced from 1% to 0.25%, thereby reducing the clogging of the M16 gas tube by half and solving the problem of difficult shell extraction. Colt also made improvements to the M16 itself, such as redesigning the buffer (i.e., the buffer spring and weight cylinder) to reduce the firing rate to a normal state; designing a maintenance tool and a new stock so that cleaning tools can be stored in the rifle; changing the twist rate from 14 inches to 12 inches; strictly controlling the production process to improve product quality. Finally, a large training program was developed on "how to properly maintain the M16," and a comic book-style rifle maintenance manual was printed and distributed to soldiers, which was the final solution to the operational issues.
Perhaps the most important change to the M16A1 was the chroming of the chamber, and later, the entire barrel. This improvement was actually proposed during the initial "par" program, but it was abandoned due to cost concerns. At that time, there was no reliable method for chroming the smaller diameter .224 barrel. The real value of chroming is to prevent corrosion in the chamber. When the chamber is rough due to rust, sand, dirt, or machining marks, the friction coefficient increases. With the lack of a pre-extraction action in the Johnson/Stoner-style bolt, and the too-small taper of the 5.56mm cartridge case, many soldiers found that the chamber would often stick after firing the first round. However, after chroming, the chamber is less prone to rusting, and friction is reduced. Any dirt remaining in the chamber is easily expelled with the cartridge case during the extraction action.
Efforts in operational performance and production issues have led to a rapid reduction in reliability issues with the M16/M16A1, although its reputation was still poor. But the M16
began to prove its reliability in combat. During August and September 1967, investigators once again surveyed soldiers' opinions on the M16 on the battlefield in Vietnam. The survey team met with over 2,100 soldiers, and only 38 expressed a desire to replace their M16 rifles, but 35 of them indicated that they wanted the XM177 type — a shortened version of the M16.
Instructions for cleaning accessories and new stocks on page 6 of the M16A1 manual
In May 1964, Colt demonstrated the reliability of the 603 model when presenting the CAR-15 family of rifles to senior officials of the U.S. Department of Defense.
A soldier from the 101st Airborne Division maintains his XM16E1 during the Vietnam War
M16A1 under maintenance
The M16A1's accessories include a dual-purpose bipod that can be used as a wire cutter in addition to being a tripod.
After addressing the frequent failure issues, the next most pressing issue was how to get more rifles into the hands of the infantry units that needed them. Until 1966, Colt was the only producer of the M16/M16A1, producing 25,000 rifles per month. On June 30, 1967, the U.S. government purchased the patents, licensing rights, and Technical Data Packages (TDPs) for the M16 rifle family, allowing them to designate other contractors to produce more rifles, enabling the military to quickly obtain large quantities of new weapons. Concerned about losing business, Colt's employees immediately launched a two-month strike to protest this decision, but the U.S. Army eventually added two more contractors to produce the M16 — the Hydramatic Division of General Motors Corporation and Harrington & Richardson — starting in April 1968, with a monthly production of 25,000 rifles each. By May 1970, the highest monthly production of the three companies reached 89,000 rifles. By 1971, General Motors and Harrington had ceased production of the M16/M16A1, while Colt continued to supply the M16/M16A1 rifles to the U.S. military until 1988. (To prevent
the cancellation of M16A1 orders, Colt actually produced two gas piston automatic principles, the Model 703, in 1969.)
The first showdown between the M16 and the AK47 was on the battlefield in Vietnam, and many reports comparing the performance of the two rifles often mention that many American soldiers, after capturing AK47s, would rather discard their M16s and use the AK47s. Because in the past, domestic media had a habit of denigrating American weapons when commenting on foreign weapons, this situation was often exaggerated, making it seem like the M16 series was very unreliable. However, the fact is that while it was true that some American soldiers dropped their M16 rifles, it was far from as widespread as people imagined. In Harold G. Moore's "We Were Soldiers Once... And Young," there are multiple mentions of how in combat, when the M16 failed, some soldiers would continue fighting with the rifles of wounded or dead soldiers, while others would squat in foxholes to fix malfunctions. Because in combat, unless their own weapon is truly unusable and there are no backup weapons, most people would not risk picking up enemy weapons under fire — that is usually something done leisurely after the battle, when cleaning up the battlefield. In addition, using different types of weapons also involves issues such as effective use of training levels and ammunition supply.
After improving the M16A1, not only did its reliability increase, but production quality was also strictly controlled. For example, before each batch of M16A1 rifles was issued to the troops, a reliability test was conducted, and the results of the test showed that the average failure rate of the M16A1 was 0.033%, lower than the specified requirement of 0.15%, and the average failure-free working time was 3000 rounds. Through strict control of the production process, the M16A1 still had good reliability. Although the M16 initially performed poorly on the battlefield in Vietnam, the problems were resolved within six months. The M16/M16A1 demonstrated in combat performance that Eugene Stoner had designed an excellent rifle. While the use of captured weapons did exist, conversely, many Vietnamese also used captured M16 series rifles. On the one hand, they were afraid of the killing power of the M16, and they often talked about the "small black gun and small bullet can make big holes." On the other hand, they used any weapons they could find, including the M16.
Although the U.S. military suffered defeat in the Vietnam War, the M16 started from the Vietnam battlefield, with Colt alone producing 3.5 million M16 rifles during this period. In fiscal year 1974, the U.S. Army purchased 2.7 million rifles. The M16 began to spread around the world and sparked a wave of small-caliber rifle fever in military forces worldwide. Interestingly, after thoroughly defeating the South Vietnamese Army, the North Vietnamese Army captured about a million M16A1 rifles from the South Vietnamese Army. Vietnam sold these captured M16A1 rifles to other places during the 1970s and 1980s, mostly to Central America, such as the Farabundo Martí National Liberation Front (FMLN) in El Salvador.
A female Vietcong patrolling by the river. The M16A1 in her hand was naturally captured from the US military.
Lieutenant P.W. Kendra, a commander of the 1st Cavalry Division who fought in Vietnam, one of the division's platoons was surrounded on a mountain, and to call for helicopter fire support, they fired signal flares. The North Vietnamese soldiers thought they were retreating, so they accelerated their attack, resulting in heavy casualties from the intense firing of the M16A1.
The scene in the movie "G.I. Jane," starring Demi Moore, where Navy SEALs put condoms on the muzzle of M16 rifles is not fictional. It is said that the instructions for the M16 state that the rifle barrel cannot be fired immediately after being submerged in water. For example, Section 8002 of the Marine Corps Marksmanship Manual (MCRP 3-01A) mentions that if the rifle barrel is submerged in water, it should not be fired directly. However, in reality, regardless of the weapon, it is best not to fire it directly after it has been submerged in water. But if carrying the firearm while swimming or diving, simply draining the water after surfacing will allow firing, and no special protection is needed. In fact, it's an old tradition for U.S. troops to put condoms on rifle muzzles. For example, in the 1980 film "The Big Red One," American soldiers are seen putting condoms on the M1 Garand rifle before landing in West Africa. The primary purpose of the condom is not to waterproof the rifle but to prevent foreign objects from entering the barrel. If sand or gravel blocks the barrel, even a reliable weapon like the AK could be dangerous, and even if it doesn't explode, it can damage the rifling. Some weapon manufacturers produce plastic muzzle caps for firearms, which are very thin and soft. Even if forgotten before firing, there won't be any regrets. For example, Austria's AUG rifle comes with plastic muzzle caps. China also provided muzzle caps for the Type 56 submachine gun during the Sino-Vietnamese War in the 1980s. These simple plastic muzzle caps are often lost, but replacements are easy to find, and no one will feel distressed. Russian soldiers would put used signal flare paper tubes on the muzzle of the AK-74. Although the M16's reliability was poor, it was not as unacceptable as people imagined. Before the Gulf War in 1991, although it was predicted that the M16 would have many problems when used in desert environments, its performance in the war was reliable and trusted by soldiers.
When the United States was deeply mired in the Vietnam War, several derivatives of the M16 emerged, including the CAR-15 series and the XM177 series, as well as two short-lived lightweight sniper rifles. One was the Colt 655, or the M16A1 Special High Profile, which added a scope mount to the standard A1-style carrying handle and used a heavy barrel. The other was the Colt 656, also known as the M16A1 Special Low Profile, which had no carrying handle and instead featured an adjustable windage mechanical sight and scope mount, with a heavy barrel and a protective ring front sight. Both rifles used the 3-9x ART scope from Leatherwood/Realist. Some models were equipped with suppressors, but these rifles were not standardized.
The Mk.4 Mod0 was another little-known variant of the M16 (Model 604) improved for the United States Navy SEALs during the Vietnam War. It was produced around 1970 to 1971 and delivered to the troops in April 1970. It differed from the standard M16 or M16A1 primarily in its improved corrosion resistance for maritime use and was pre-equipped with a suppressor. Most parts were coated with a layer of Kal-Guard lubricant, and a 1/4-inch diameter hole passed through the buttstock and buffer tube for drainage, with an O-ring reinforcing the attachment of the buffer components. It was said that this model could be carried in water up to 200 feet (about 60m) deep without damage. The initially used Mk.2 Mod 0 "muzzle blast suppressor" was based on the M4 suppressor from the Army's Human Engineering Lab (HEL). If the HEL M4 suppressor was used, the gas energy in the gas tube would be reduced, requiring a redesign of the receiver and the addition of a gas deflector on the charging handle to prevent escaping gas from hitting the shooter during firing (both the AR/M16 rifles had this drawback, and if a suppressor was installed, it was best to replace it with a larger charging handle with a gas block). As a result of this improvement, the rifle could fire semi-automatic or fully automatic when equipped with the HEL M4 suppressor, but if the HEL M4 suppressor was removed, manual loading was required after each shot. The Mk.2 Mod 0 suppressor, although an integral part of the Mk.4 Mod0 rifle, was already improved so that the rifle could still function normally even if the suppressor was removed. The Mk.2Mod 0 suppressor had a bayonet mount, but it was useless on the Mk.4 Mod0 rifle due to the protective ring front sight.
Model655 Special High Profile
The same flat-top receiver M16 used in the Vietnam War, but the scope installed is the M84
The flat-top receiver (above) or the model with a carrying handle can be equipped with an AN/PVS-2 night vision scope
The rear end of the HEL M4
The appearance and structure of the HEL M4 silencer. The flame arrester needs to be removed when installing this silencer.
M16 with HEL M4 silencer during the Vietnam War
When installing a silencer, you need to install this gunpowder gas deflector called Gas Shield
The Mk2 muffler produced by KAC has a drainage hole at the rear. Perhaps the picture above is the shape of the Mk4 MOD0
The silenced M16 on display in the Navy Seal Museum. The one on the left is the KAC Mk2 silencer, and the one on the right is probably the modified HEL M4 silencer.
The KAC Mk2 silencer was actually used in the M4A1 era
M16A1 with FA-XM silencer
The Barska 4x20 scope was already in use during the Vietnam War
M16A1.jpg)
This is a civilian AR-15 part, so that civilian guns cannot be converted into full-automatic
Navy SEALs in Vietnam
Some people also use the method of reverse-tying parallel magazines
The M16A1 has not been completely retired, at least TRADOC (US Army Training and Doctrine Command) is still in use. This is a US soldier undergoing basic training at Fort Lee, Virginia, on July 11, 2006.
Competitors at the 2001 "Best Ranger" competition used the M16A1 as a training gun in the competition.
Vietnam captured a large number of M16A1s during the war and has been refurbishing and using them to this day.
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