The Army is also upgrading its existing M4s to a new M4A1 standard.
The M4 still has its critics, including a retired major general, who have derided this descendant of the M16 as inadequate for modern ground forces. They point to the direct impingement gas operating system, which siphons off hot gases from burning gunpowder to chamber the next round, as guilty of fouling the inside of the rifle, increasing the likelihood of jams. They also deride the 5.56-millimeter round as having insufficient stopping power and believe the M4’s barrel is not thick enough to avoid overheating in sustained fire.
The U.S. Army is an armed force with a truly global reach. At any given time, America’s premier land power operates on several different continents simultaneously, from hot, dry deserts to humid jungles and sprawling cities. Its infantrymen carry a weapon whose lineage dates back to Vietnam but which has been constantly improved to become the weapon it is today. Rugged, simple and accurate, the M4 carbine is the standard infantry weapon of not just the Army but all of America’s ground forces.
The story of the M4 goes back to the mid-sixties and the early days of the Vietnam War. The Pentagon, mulling sending hundreds of thousands of troops to South Vietnam, wanted a small, lightweight service rifle to replace the larger standard-issue M14. The new AR15, or Armalite Rifle-15, was smaller, lighter and fired a smaller 5.56-millimeter bullet. A soldier carrying the AR15, later designed the M16, could carry twice as much ammunition as a soldier carrying the M14. Demographic trends also meant that more and more soldiers were coming from cities and unfamiliar with firearms, and the M16 with less recoil was easier to train soldiers to proficiency.
Despite earlier battlefield success, once fielded in large numbers the M16 quickly started racking up complaints. A last-minute change in propellant powder, as well as the erroneous belief that the rifle never needed cleaning, caused many jams on the battlefield. Although the problems were eventually sorted out and an improved version, the M16A1, was fielded in 1967, the weapon developed a reputation as being an unreliable weapon. In the mid 1980s the A1 was replaced with the M16A2, which featured a thicker barrel and three round burst capability.