Colt M16A2 Rifle Weapons System

The development of the M16A2 rifle was originally requested by the United States Marine Corps as a result of combat experience in Vietnam with the XM16E1 and M16A1.  It was officially adopted by the Department of Defense as the "US Rifle, 5.56 mm, M16A2" in 1982. The Marines were the first branch of the U.S. Armed Forces to adopt it, in the early/mid-1980s, with the United States Army following suit in the late 1980s. The weapon's reliability allowed it to be widely used around the Marine Corps' special operations divisions as well.

Modifications to the M16A2 were extensive. The flash suppressor was again modified, this time to be closed on the bottom so it would not kick up dirt or snow when being fired from the prone position, and acting as a recoil compensator.

A spent case deflector was incorporated into the upper receiver immediately behind the ejection port to prevent cases from striking left-handed users.  The action was also modified, replacing the fully automatic setting with a three-round burst setting.  When using a fully automatic weapon, inexperienced troops often hold down the trigger and "spray" when under fire. The U.S. Army concluded that three-shot groups provide an optimum combination of ammunition conservation, accuracy, and firepower.  The USMC has retired the M16A2 in favor of the newer M16A4; a few M16A2s remain in service with the U.S. Army Reserve and National Guard, Air Force, Navy and Coast Guard.

The handguard was modified from the original triangular shape to a round one, which better fit smaller hands and could be fitted to older models of the M16. The new handguards were also symmetrical so armories need not separate left- and right-hand spares. The handguard retention ring was tapered to make it easier to install and uninstall the handguards. A notch for the middle finger was added to the pistol grip, as well as more texture to enhance the grip. The butts-tock was lengthened by 5⁄8 in (15.9 mm). The new buttstock became ten times stronger than the original due to advances in polymer technology since the early 1960s. Original M16 stocks were made from cellulose-impregnated phenolic resin; the newer stocks were engineered from DuPont Zytel glass-filled thermoset polymers. The new stock included a fully textured polymer butt-plate for better grip on the shoulder, and retained a panel for accessing a small compartment inside the stock, often used for storing a basic cleaning kit.  (Wikipedia)