The M16 rifle (officially designated Rifle, Caliber 5.56 mm, M16) is a family of military rifles adapted from the ArmaLite AR-15 rifle for the United States military. The original M16 rifle was a 5.56×45mm automatic rifle with a 20-round magazine.
In 1964, the M16 entered US military service, and the following year was deployed for jungle warfare operations during the Vietnam War. In 1969, the M16A1 replaced the M14 rifle to become the US military’s standard service rifle. The M16A1 incorporated numerous modifications including a bolt-assist, chrome-plated bore, protective reinforcement around the magazine release, and revised flash hider.
After modifications, the new redesigned rifle was subsequently adopted as the M16 Rifle.
(The M16) was much lighter compared to the M14 it replaced, ultimately allowing soldiers to carry more ammunition. The air-cooled, gas-operated, magazine-fed assault rifle was made of steel, aluminum alloy, and composite plastics, truly cutting-edge for the time. Designed with full and semi-automatic capabilities, the weapon initially did not respond well to wet and dirty conditions, sometimes even jamming in combat. After a few minor modifications, the weapon gained in popularity among troops on the battlefield.
Despite its early failures the M16 proved to be a revolutionary design and stands as the longest continuously serving rifle in US military history. It has been adopted by many US allies and the 5.56×45 mm NATO cartridge has become not only the NATO standard but “the standard assault-rifle cartridge in much of the world.” It also led to the development of small-caliber high-velocity service rifles by every major army in the world. It is a benchmark against which other assault rifles are judged.
In February 1967, the improved XM16E1 was standardized as the M16A1. The new rifle had a chrome-plated chamber and bore to eliminate corrosion and stuck cartridges, and other minor modifications. New cleaning kits, powder solvents, and lubricants were also issued. Intensive training programs in weapons cleaning were instituted including a comic book-style operations manual. As a result, reliability problems greatly diminished and the M16A1 rifle achieved widespread acceptance by U.S. troops in Vietnam.
In 1969, the M16A1 officially replaced the M14 rifle to become the U.S. military’s standard service rifle.