The M16 rifle (officially designated Rifle, Caliber 5.56 mm, M16) is a family of assault 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 … 展开

The M16 is a lightweight, 5.56 mm, air-cooled, gas-operated, magazine-fed assault rifle, with a rotating bolt. The M16's receivers are made of 展开

In March 1970, the U.S. recommended that all NATO forces adopt the 5.56×45mm cartridge. This shift represented a change in the philosophy of the military's long-held position about caliber size. By the mid 1970s, other armies were looking at … 展开

Colt Commando (XM177 & GAU-5)
In Vietnam, some soldiers were issued a carbine version of the M16 named XM177. The XM177 had a shorter 10 in (254 mm) barrel and a telescoping stock, which made it substantially more compact. It also possessed a … 展开

Background
In 1928, a U.S. Army 'Caliber Board' conducted firing tests at Aberdeen Proving Ground and recommended transitioning to smaller caliber rounds, … 展开

During the early part of its service, the M16 had a reputation for poor reliability and a malfunction rate of two per 1000 rounds fired. The M16's action works by passing high-pressure propellant gasses, tapped from the barrel, down a tube and into the carrier group … 展开

M16
This was the first M16 variant adopted operationally, originally by the U.S. Air Force. It was equipped with triangular handguards, buttstocks without a compartment for the storage of a cleaning kit, a three-pronged … 展开