In December of 1959, Colt acquired manufacturing and marketing rights to the AR-15. In 1962 Colt was able to get the Department of Defense's Advanced Research Project Agency (ARPA) to test 1,000 weapons in its Vietnam-oriented Project Agile. An enthusiastic report led to more studies from the Department of Defense and the Department of the Army, and despite strong Army opposition, Defense Secretary McNamara ordered 85,000 M16's for Vietnam, and 19,000 for the Air Force.
However, early reports showed that the M16 was not living up to expectations. These reports, presented to McNamara by the Ordnance Department, showed the M16 having reliability as well as accuracy problems. These reports in turn praised the Ordnance Department's own M14. While the M14 performed well, it was too heavy for the hot jungles of Southeast Asia, and its ammunition also would not allow more than 50-100 rounds to be carried on patrols, severely limiting its capabilities as an automatic weapon.
Further evaluation of the M14 and M16 was done by an independent agency. It concluded that M14 was not as bad as had been suggested by some, that the AR-15 itself was not as good as its proponents had represented it to be. However, they did note that the AR-15 had greater capability for improvement, and that its small size and weight made it a handier weapon in Vietnam.
The M16 was issued w/o proper training and inadequate cleaning supplies. Combined with the humid jungle of Southeast Asia, this caused problems and the rifle gained a bad reputation. Because tolerances were tighter than in previous military arms, the M16 had to be kept extremely clean. War correspondents filed reports where the M16 was jamming, and many were shown on the evening news. It was reported that our soldiers were being killed by a faulty rifle.
This led to Congressional investigations which turned up two related problems. First, the cleaning issue. As training was provided, supplies issued, and some redesign, M16 performed more reliably. The second issue dealt with the use of ball propellants instead of IMR propellants. Remington had developed the 5.56mm round using one type of powder, but the specification was changed during military contract production to allow an alternate. This powder caused more fouling and increased the rate of fire.
The replacement of the powder, combined with a new buffer to slow rate of fire, a chrome plated chamber and barrel to improve rust resistance, a closed prong flash-hider, forward bolt assist, new buttstock w/storage for cleaning kit, and introduction of a 30-shot magazine was adopted as the M16A1 and performed well for the duration of the 60's and 70's. This rifle was also produced by GM and Harington & Richardson during Vietnam era as well as other countries including the Philippines.
In the late 1970's, the Army re-examined it's rifle situation. Existing M16s were well worn, and the current programs that were looking into a replacement for the M16 were not far enough along. So in 1978, the M16 underwent a Product Improvement Program.
The results were an increased barrel diameter, and one whose rifling was changed from 1:12 to 1:7 to accommodate the new round, developed by Belgium's Fabrique Nationale, the SS109. This round extended the range of the rifle, and propelled a 62gr bullet with a steel core at over 3000 fps. The rear sight was modified to allow more accurate adjustments of windage by hand, as well as for elevation calibrated out to 800 meters. It incorporated a case deflector to prevent brass from hitting left-handed firers, and new round handguards to replace the older triangular design. Also, full-auto capability was replaced with a three-shot burst. This allowed for more controlled firing, as well as greater accuracy as all three rounds are downrange before the effects of recoil can impact their path. This new rifle was adopted as the M16A2.
In 1994, the U.S. Army officially adopted its second carbine of the 20th century. Though carbine versions of the M16 had been used all along (as the XM177 as well as the CAR-15), demand for these was limited to select groups. With the increase in the use of Special Operations forces during and after the Cold War, the demand for a shorter, lightweight weapon was increased.
The M4 was developed by Colt's Manufacturing Company, and is intended to be used by Special Operations forces as well as other select members of the military. It is designed to replace a variety of carbines and SMGs in the Army's arsenal, as well as to repeat the accuracy and reliability of the M16A2. It uses a 14.5" barrel, and a four-position telescoping stock while maintaining the ability to mount an M203 grenade launcher. In the collapsed position, it measures under 30 inches, and weights just over 5 1/2 pounds, with an effective range of 600 meters. The M4 is available with 3-shot bursts (M4) as well as full-auto capabilities (M4A1).
Both versions of the M4 are equipped with a Picatinny-Weaver Rail system to replace the carry handle. This allows for a variety of sighting systems to be mounted atop the receiver, from the standard handle with A2 sights to night-vision devices, scopes, and lasers.
Current military inventory includes: