M16 (rifle)

M16 is the U.S. Military designation for a family of rifles derived from the Armalite AR-15. It is an assault rifle which fires NATO standard 5.56 mm ammunition. It has been the primary infantry rifle of the United States military since 1967, is in use by 15 NATO countries, and has been the most produced firearm in its caliber.

History

Project SALVO

In 1948, the Army organized the civilian Operations Research Office (ORO), mirroring similar operations research organizations in Britain. One of their first efforts, Project ALCLAD, studied body armor and quickly concluded that they would need to know considerably more about battlefield injuries in order to make reasonable suggestions. Over 3 million battlefield reports from WWII were analyzed, and over the next few years they released a series of reports on their findings.

Related Topics:
Operations research - Body armor

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Their basic conclusion was that the vast majority of combat takes place at short ranges. In a highly mobile war combat teams ran into each other largely by surprise, and the team with the higher firepower tended to win. They also found that the chance of being hit in combat was essentially random -- that is, accurate "aiming" made little difference because the targets no longer sat still. The number one predictor of casualties was the total number of bullets fired.

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These conclusions suggested that infantry should be equipped with a fully automatic rifle of some sort, in order to increase the rate of fire. However, it was also clear that such weapons dramatically increased ammunition use, in order for a rifleman to be able to carry enough ammunition for a firefight, they would have to carry something much lighter.

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For both of these reasons, existing rifles were poorly suited to real-world combat. Although it appeared the new T44 (precursor to the M14) would increase the rate of fire, its heavy ammunition made carrying enough of it a real problem. Moreover the length and weight of the gun meant it was not really suitable for short range combat, where a smaller and lighter weapon could be brought to bear much more quickly.

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These efforts had not gone unnoticed by René Studler, U.S. Army Ordnance's Chief of Small Arms Research and Development. He was upset about the civilian agency that was treading on "his" turf, and started an effort to support the "full power" round developed for the T25, Springfield Armory's competitor to the T44. In the end, he asked the Aberdeen Proving Ground to submit a report on the smaller caliber weapons.

Related Topics:
Springfield Armory - Aberdeen Proving Ground

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This plan backfired when his assigned research lead, Donald Hall, found that a .22 in (5.59 mm) round would have equal performance to larger rounds in most combat situations. With the higher rate of fire possible due to lower recoil, it was likely such a weapon would inflict more casualties on the enemy. His team members, notably William C. Davis Jr. and G.A. Gustafson, started development of a series of experimental .224 in (5.69 mm) rounds. In 1955, their request for further funding was denied.

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A new study, Project SALVO, was set up to try to find a weapon design suited to real-world combat. Running between 1953 and 1957 in two phases, SALVO eventually suggested that a weapon firing four rounds into a 20 in (0.5 m) area would have double the hit probability of existing semi-automatic weapons.

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In the second phase, SALVO II, several experimental weapons concepts were tested. Irwin Barr of AAI introduced a series of flechette weapons, starting with a shotgun shell containing 32 darts and ending with single-round flechette "rifles". Winchester and Springfield offer multi-barrel weapons, while ORO's own design used two .22, .25 or .27 bullets loaded into a single .308 or .30-06 cartridge.

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Eugene Stoner

Meanwhile testing of the T44 continued, and Fabrique Nationale via the American firm of Harrington & Richardson also submitted their new FN FAL into testing as the T48. However, the results of the testing were apparently already a forgone conclusion; the T44 was selected as the new battle rifle for the U.S. Army.

Related Topics:
Fabrique Nationale - FN FAL

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But this did not occur before a newcomer seriously upset the contest. In 1954, Eugene Stoner of the newly-formed ArmaLite started development of the AR-10. Springfield's T44 and similar entries were conventional in every meaning of the term, using wood for the "furniture" and otherwise built entirely of steel. ArmaLite was founded specifically to bring the latest in designs and alloys to firearms design, and Stoner felt he could easily beat the other offerings.

Related Topics:
Eugene Stoner - ArmaLite - AR-10

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Stoner's design was radical. The barrel was composite, consisting of a thin steel liner carrying the rifling, inside an aluminum alloy tube giving it strength. The receiver was made of forged and milled aluminum instead of steel. The barrel was mated to the receiver by a separate hardened steel adapter to which the bolt locked. This allowed a lightweight aluminum receiver to be used while still maintaining a steel-on-steel lockup. The bolt was operated by gases vented from the front of the barrel directly into a cylinder created in the bolt carrier with the bolt itself acting as a piston. Traditional rifles located this cylinder and piston close to the gas vent. The stock and grips were made of plastic instead of wood and even the flash hider was lightened by making it out of titanium.

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Meanwhile the layout of the gun itself was also radically changed. Typical designs placed the sights directly on the barrel, using a bend in the stock to transfer the recoil to the shoulder. However this meant that the gun wanted to rise when fired, making it very difficult to control. Stoner's solution to this problem was to place the barrel in line with the stock, well below eye level, and then raise the sights up. The rear sight's carrier doubled as a convenient carrying handle.

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The AR-10 was by far the most advanced design in the world at the time. At over two pounds (900 g) lighter than the competition and with much better recoil control, it should have easily won the contest. However, it was entered late and somewhat rushed, and the odd layout found few followers among the traditionalist big-round players. When a barrel burst in testing, the AR-10 was largely written off.

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CONARC

In 1957, a copy of Gustafson's funding request from 1955 found its way into the hands of General Willard Wyman, commander of the U.S. Continental Army Command (CONARC). He immediately put together a team to develop a .22 caliber weapon for testing. Their finalized request called for a select-fire weapon of 6 pounds (2.7 kg) when loaded with 20 rounds of ammunition. The bullet had to penetrate a standard U.S. steel helmet, body armor, or a 0.135 inch (3.4 mm) steel plate at 500 yards (460 m), while equaling or exceeding the "wounding" ability of the .30 Carbine.

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Having seen the AR-10 earlier, Wyman personally suggested that ArmaLite enter a weapon for testing. Stoner was working on a newer version of the AR-10 (the AR-16), but others at the company took up the challenge. Their first design, using conventional layout and wooden furniture, proved to be too light. When combined with a conventional stock, recoil was again a problem even with the light rounds. Their second design was simply a scaled-down AR-10, and immediately proved to be much more successful. Winchester entered a design based on their M1 Carbine, and Earle Harvey of Springfield attempted to enter a design, but was overruled by his superiors at Springfield, who refused to divert resources from the T44.

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In the end ArmaLite's AR-15 really had no competition. The lighter round allowed it to be scaled down even smaller than the AR-10, and even after replacing the barrel with a simpler all-steel one, it was still well over a pound (450 g) lighter than the Winchester at 2.89 kilograms empty, about 3.5 kg loaded.

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Its only major problem was that it wasn't fully developed before Army testing began nine months later on March 31st, 1958. Rainwater caused the barrels of both the ArmaLite and Winchester rifles to burst, causing the Army to once again press for a larger round, this time at .258 in. Nevertheless, they suggested continued testing for cold-weather suitability in Alaska. Stoner was later asked to fly in to replace several parts, and when he arrived he found the rifles had been improperly reassembled. When he returned he was surprised to learn that they too had rejected the design even before he had arrived, their report also "surprisingly" suggested the .258 round. After reading these reports, General Maxwell Taylor became dead-set against the design, and pressed for continued production of the M14.

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Not all the reports were negative. In a series of mock-combat situations testing the AR-15, M14 and AK-47, Army testing found that the AR-15's small size and light weight allowed it to be brought to bear much more quickly, just as CONARC had suggested. Their final conclusion was that an 8 soldier team equipped with the AR-15 would have the same firepower as a current 11 soldier team armed with the M14. They also found that the AR-15 was more reliable than the M14, suffering fewer stoppages and jams in tests where thousands of rounds were fired.

Related Topics:
M14 - AK-47

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At this point Fairchild had spent $1.45 million in development expenses, and there was no end in sight. Fairchild sold production rights for the AR-15 to Colt Firearms in December 1959, for only $75,000 cash and a 4.5% royalty on subsequent sales. In 1960 Armalite was reorganized, and Stoner left the company.

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M16 adoption

A demonstration of the AR-15 was made to Curtis LeMay in June 1960. He immediately ordered 8,500 for defense at Strategic Air Command airbases. Colt Industries also approached the Advanced Research Projects Agency (ARPA), who bought 1000 rifles for use by South Vietnamese troops in the early summer of 1962. American special operations units working with the South Vietnamese troops filed remarkable battlefield reports, pressing for its immediate adoption.

Related Topics:
Curtis LeMay - Strategic Air Command - Advanced Research Projects Agency - Special operations

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U.S. Secretary of Defense Robert McNamara now had two conflicting views: the ARPA report favoring the AR-15 and the Pentagon's position on the M14. Even President John F. Kennedy expressed concern, so McNamara ordered Secretary of the Army Cyrus Vance to test the M14, the AR-15 and the AK-47. The Army's test report stated only the M14 was suitable for Army use, but Vance wondered about the impartiality of those conducting the tests. He ordered the Army Inspector General to investigate the testing methods used, who reported that the testers showed undue favor to the M14.

Related Topics:
Secretary of Defense - Robert McNamara - John F. Kennedy - Cyrus Vance

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McNamara ordered a halt to M14 production in January 1964. In November, the Army ordered 85,000 XM16E1s for experimental use, and the Air Force ordered another 19,000. Meanwhile the Army carried out another project, the Small Arms Weapons Systems (SAWS), on general infantry firearm needs in the immediate future. They highly recommended the immediate adoption of the weapon, so much so that they started referring to it as the M16. Later that year the Air Force officially accepted their first batch as the United States Rifle, Caliber 5.56 mm, M16. The Air Force M16s were different from the Army XM16E1s, which had a forward assist, as described below. The Air Force M16s were slightly modified AR-15s.

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When the M14 reached Vietnam with U.S. troops in 1965 its flaws were instantly recognized. It was far too cumbersome and too heavy to use effectively in a close-quarters jungle environment, and the heavy ammunition meant only small quantities were carried on patrol. The fully automatic fire quickly demonstrated itself as useless, as the British had suggested, and the rifles were eventually delivered locked in semi-automatic. In the end the Army had spent a considerable amount of time and money switching from one semi-automatic weapon to another, and it appeared this happened largely due to internal politics. In defense of the M14 design, it was lighter and more reliable than the M1 Garand from which it evolved. While the M16 had the TCC and numerous changes to enhance its reliability, the M14 received no such attention. The Army chose to freeze the M14's design at an undeveloped stage.

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Meanwhile the troops desperately tried to increase their own firepower in the face of the Viet Cong's Soviet-designed AK-47s. They took to scrounging any weapon they could find, the pre-WWII Tommy gun became particularly well-used. The XM16E1 was being introduced in increasing numbers, but quickly gained a bad reputation.

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With the XM16E1 the Pentagon had demanded a change in the cartridge's propellant from the coarse-grained Improved Military Rifle (IMR) to the finer grained "ball" powder, which increased the automatic firing rate but also increased fouling of the bore and consequently caused the rifle to jam. To correct this, a "forward assist" plunger device to close the bolt in case of a misfeed was added. Colt, the Air Force, the Marine Corps and Eugene Stoner all agreed this device needlessly complicated the rifle and added about $4.50 to its procurement cost with no real benefit, but after another three years the Army ordered 840,000 of this version on February 28th, 1967. The version became known as the M16A1.

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Colt had oversold the M16's reliability during testing, to the point where they claimed it never had to be cleaned. While this may have been true with the original IMR powder the rifle was developed with, it was not the case with the more finely-grained, faster-burning ball powder that was considerably "dirtier". The direct impingement gas operating system used a tube along the top of the barrel that vented gas back into a 'piston' formed behind the bolt and the recess in the bolt carrier. When combustion gases reached this area, they drove the bolt carrier to the rear and then vented the excess gas out the ejection port and out between the gas key at the top of the bolt carrier and the gas tube from the port in the barrel. Conventional designs keep the piston above or below the barrel and vent excess gas at that point. The advantage of the Stoner system was that the 'piston' formed by the bolt and bolt carrier operated in a direct line and on the same axis as the bore of the rifle. This resulted in no adverse movement of the bore axis due to the movement of the bolt carrier assembly. The adverse result of this design is that when the propellant gas is traveling down the tube, it cools and condenses becoming solid carbon. This carbon builds up in the action of the gun quickly. The M-16 therefore requires frequent cleaning to remain reliable.

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Making matters worse, troops were told the weapon required no cleaning because of its space age construction, and had not been supplied with cleaning kits. In the field the guns started jamming all the time. Soldiers often derisively referred to them as "toy guns" and used the catch phrase "You can tell it's Mattel" when one malfunctioned. This later blossomed into an urban legend that the first M16s were actually manufactured by the toy giant.

Related Topics:
Space age - Catch phrase - Mattel - Urban legend - Toy

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The M16 debate once again took off, both in the Army and in Washington, DC. Stoner's latest design, a family of weapons known as the Stoner 63, were sent to Vietnam for testing, while the SPIW flechette test weapon program was re-activated.

Related Topics:
Washington, DC - Stoner 63 - SPIW

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Luckily cooler heads prevailed. Cleaning kits were quickly produced, and a comic book was circulated among the troops to demonstrate proper maintenance. The reliability problems disappeared almost overnight, although the reputation did not. This did not appear to be true for the North Vietnamese troops, however, who started to use the rifle whenever one could be found.

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Perhaps the most important change to the M16A1 was the introduction of chrome plating in the chamber, and some time later, the barrel as well. This improvement had been suggested in the original SALVO tests, but was dismissed as not cost-effective or practical. At the time, no reliable way had been devised to chrome-plate a .224" diameter barrel. The true value of Chrome Plating is preventing corrosion in the Chamber. Being a nearly straight-walled chamber, the slightest quantity of rust, corroded brass, sand, fouling, or even machining marks increase friction exponentially. Soldiers in the field found that the first round nearly always fired but would stick in the chamber. This is why the AK-47 was designed with a tapered chamber. Chrome lining not only prevents rust, but it also decreases friction. Fouling that does get into the chamber is pressed into the side of the fired case and ejected along with it.

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After its rocky start, the M16 has proven itself to be one of the more reliable combat rifles. By the end of 1967, the troops, when asked, would only trade in their M16s for the XM177, a carbine version of the same weapon.

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The lightweight round was likewise a matter of much debate in the rifle community. The "big round" concept refused to die for many years, and calls for an increase in caliber continued into the 1980s. Much of the debate centered on the Soviet Union's use of a larger StG44-style cartridge, the 7.62 x 39 mm, cut down from their wartime 7.62 x 54 mmR "full power" design. The debate ended for good when in the early 1970s the USSR introduced their own small round, one even smaller than the M16 at only 5.45 x 39 mm. Apparently SALVO had the right idea all along.

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NATO standardization

In March 1970, the Pentagon shocked other NATO nations by stating all U.S. forces assigned to NATO would be equipped with the M16A1. The British military was highly vocal in voicing its anger after being thrashed by American Ordnance personnel into adopting the 7.62 mm NATO round because their .280 caliber round wasn't effective enough nearly twenty years earlier. Now they were being told the U.S. recognized the need for such a caliber of firearm after all, and was willing to start the NATO standardization of a lighter round after all.

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But by the middle of the 1970s other armies were also looking at an M16 style weapon. A NATO standardization effort soon started, and tests of various rounds were carried out starting in 1977. The U.S. offered their original design, the M193, with no modifications, but there were serious concerns about its penetration in the face of the wider introduction of body armor. The British introduced a modified 5.56 mm round, using a longer and thinner bullet of 4.85 mm, mounted in the existing U.S. cartridges. The round had somewhat better ballistics, and considerably better penetration, able to reach 600 m and meet their requirements for a squad automatic weapon (small machine gun). The Germans introduced a new 4.7 mm caseless round, which was considerably lighter while offering similar ballistics to the original U.S. design. However, there was considerable distrust of the system due to the possibility of "cook off". A final design was offered by the Belgians, the SS-109, a new round also based on the U.S. cartridge and a new bullet with the same 5.56 mm caliber, but with a small tip of steel to improve penetration.

Related Topics:
Body armor - Machine gun

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Testing soon showed that the British and Belgian designs were roughly equal, both outperforming the original U.S. design. In order to get full performance from the SS-109, however, the barrels would have to use a 1-in-7 twist in the rifling, and in the existing 1-in-9 it offered almost no advantage over the M193. In the end, it appears that the Belgian round was an easier sell to the U.S. Army, even though either round would require all-new rifles. The resulting M16A2, introduced in 1982, has been the standard U.S. military rifle since then.

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After all of the debate, the M16 is still considered to be one of the best combat rifles ever produced. Total world-wide production is about 8 million.

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