The story of the M16 family of rifles begins with Eugene Stoner, an engineer and former Marine armorer who created the ArmaLite AR-10 in 1956. The AR-10 was chambered in the standard 7.62x51mm NATO cartridge, but the subsequent year’s smaller AR-15 and its .223 Remington cartridge would be the design that would completely revolutionize the modern service rifle. ArmaLite’s sale of the AR-10 and AR-15’s rights to Colt would lead to product refinements, and the standardization of the .223 cartridge as the 5.56x45mm NATO round. The AR-15 would be adopted by the Department of Defense in 1962 and designated the M16 in 1963; production of various experimental models would soon follow.

M16

The M16 did not have a forward assist, and would only be tested by the Marine Corps (NMMC).

The USMC would decide to adopt the M16 in 1966 (NMMC).

The early 1960s would see the M14 standardized as the common service rifle by the Department of Defense, with the goal of replacing the M1 Garand, M1 Carbine and M1918A2 Browning Automatic Rifle as a “one size fits all” weapon. This would lead to a design that underperformed in nearly all scenarios, and almost immediately the door for a replacement had opened. The Marine Corps would begin testing the M16 in the early 1960s, but would not field this version of the rifle in Vietnam. The M16 did not have a forward assist, and while this was not problematic to the USMC, the army would insist on one being added. This led to the creation of the XM16E1, an M16 with forward assist incorporated into the upper receiver. Some Marine Corps units would test the XM16E1 in Vietnam while others the Stoner 63. Ultimately, the XM16E1 would be determined to be the best design to replace the M14.

An article by By Lt. Colonel J.W. Gibbs III, U.S. Marine Corps, (Retired) in Small Arms Review details L Company, 3rd Battalion, 3rd Marines testing the Stoner 63 Carbine and Light Machine Gun in Vietnam. While there were some initial problems, the rifles “broke in” and were considered superior to the XM16E1.

XM16E1

The XM16E1 would be the first M16 type rifle fielded by the USMC.

The III Marine Amphibious Force in Vietnam would replace their M14s with XM16E1s in the early months of 1967. Unfortunately for the average Marine grunt issued the new rifle, many lay ahead. A prevailing belief that M16s were “self cleaning,” coupled with inadequate cleaning gear resulted in Marine rifleman having their XM16E1s go down in the heat of battle. The causes of this were numerous, including a change in cartridge powder that allowed carbon to build up much faster. The lack of proper maintenance equipment and training led to excessive wear in a short period of time, often to the barrel. Reports from the battlefield that malfunctioning weapons were directly leading to deaths meant further revisions were in order. By the time the Marine Corps began fielding the XM16E1, the improved M16A1 was already in the works. This led to a very short shelf life for XM16E1 rifles, as the M16A1s began flowing into the hand of Marines and soldiers in mid to late 1967.

The lack of cleaning gear and proper maintenance instructions would plague the XM16E1 in Vietnam (USMC).

Marines with XM16E1s. The attached grenade launcher was known as the XM148 (USMC).

Marines in Hue City (Left) and Khe Sanh (Right) with XM16E1s in early 1968. Photos of Marine in these marquee battles show a mix of XM16E1s and M16A1s, which had already began to be issued by 1968. Of not the Marine in the far right is fielding an M16A1 lower with an XM16E1 upper (USMC).

1967 would see the Marine Corps transition away from the M14 and M70 to the XM16E1 and M40 (Plowman collection).

M16A1

The growing pains of the M16 family of rifles would begin to work their way out with the M16A1. The M16A1 would incorporate design features that were initially recommended by Eugene Stoner but rejected by the Department of the Army, most notably the chroming of the chamber and bore of the barrel. Less critical upgrades included the addition of a heavier buffer to control the cyclic rate of fire and mitigate jamming issues, a fence being added around the magazine release to prevent accidental engagement, and a birdcage flash hider to prevent snagging on vegetation while on patrol. Perhaps just as important detailed cleaning instructions and adequate cleaning gear were issued to the individual soldier and Marine, preventing many of the failures to feed, fire or eject that plagued the XM16E1.

Marines in Hue City and Khe Sanh with M16A1s (USMC).

American forces in Vietnam were issued a comic book style rifle maintenance manual to teach proper cleaning and lubrication techniques for the M16A1 (NARA).

By late 1967, Marines in Vietnam began to be issued the M16A1. Photographs from the fighting in Hue City and Khe Sanh during the Tet Offensive of early 1968 show a mix of M16A1s and XM16E1s in the hands of Marines, with progressively less XM16E1s seen as time went on. The M16A1 would prove to be far superior to its predecessor, and the new rifle would really begin to come into its own as field performance increased. In 1969, the USMC would adopt the M16A1 as the branch’s standard service rifle. 1969 would also mark the beginning of the drawdown of American forces in Vietnam. The 3rd Marine Division would leave that fall, and a year and a half later in 1971 the 1st Marine Division would follow. Marine advisors and embassy guards would remain until 1975, and the M16A1 would serve the Marine Corps well for the remainder of the Vietnam War, with the problems experienced in 1967 significantly reduced.

The M16A1 was produced by Colt, Harrington & Richardson, and the Hydra-Matic Division of General Motors. G.M. would produce around 470,000 M16A1s, while HRA would produce over 246,000. Colt would produce the vast majority, well into the millions.

The M16A1 would be adopted as standard in 1969. Images from the later years of the Vietnam War show Force Recon Marines having applied camouflage paint to the handguards and stocks of some of their rifles. Photos also show the transition to the newer 30 round magazines (USMC).

After the conclusion of the Vietnam War, the Marine Corps would begin considering ways to improve the M16A1. The chief complaint was lack of accuracy, and the USMC would examine the best ways to move the M16 platform forward in this regard. The M16A1 had very rudimentary sights, and while they were mechanically excellent at retaining their Battlesight Zero (BZO), they were not easily adjusted. The very lightweight “pencil” profile of the barrel also did not help in regards to accuracy. The Marine Corps, with the highest standards for accuracy in the US military, would be the driving service to see these deficiencies improved, leading to the creation of the M16A2.

Marine recruits on the rifle range learning to fire the M16A1. The lack of accuracy and precision of the M16A1 would become apparent in the years following the Vietnam War (USMC).

The M16A1 would serve in combat with the USMC during Operation Urgent Fury in Grenada and in Beirut in 1983. Shortly after, the M16A2 would replace the M16A1 as the standard service rifle (USMC & NARA).