After Vietnam, the M16A1 continued to serve as the U.S. military’s service rifle through the early 1980s during years that were often turbulent. When the 24th Marine Amphibious Unit joined the peacekeeping mission in Beirut, Lebanon, in late 1982, the M16A1 was there. When a force of nearly 10,000 U.S. soldiers, sailors, airmen and Marines participated in the Operation Urgent Fury invasion of Grenada in late 1983, the M16A1 was there again. At that point, the M16 was about to undergo yet another change. Three years earlier, NATO member nations had ratified Standardization Agreement 4172 (or “STANAG 4172”), which formally adopted the 5.56x45 mm cartridge as the chambering for all NATO rifles. Although the new cartridge carried similarities over from the 5.56 mm M193 round, it utilized a heavier 62-grain bullet with a steel core to give the load greater penetration. Designed by Belgium’s Fabrique Nationale as the SS109, it was the cartridge standardized as 5.56x45 mm NATO or the M855 to the U.S. military.

In November 1983, the U.S. Marine Corps adopted a product-improved version of the M16A1 chambered for the 5.56x45 mm NATO round. The new rifle was called the M16A2 and it differed significantly from its predecessor: improved rear sights, a brass deflector, a heavier barrel and 1:7-inch rifling were among the changes. The M16A2 also replaced the M16A1’s “AUTO” selector setting with a “BURST” setting delivering three rounds with every trigger pull. The Army followed the Marine Corps’ adoption of the improved rifle in March 1986 when it ordered 100,176 M16A2 rifles from Colt. In September 1988, the U.S. government placed an initial order for 266,961 M16A2s with Fabrique Nationale’s North American subsidiary, FN Mfg., Inc. of Columbia, S.C. Late the following year, when 57,000 U.S. military personnel conducted the Operation Just Cause invasion of Panama, the M16A2 was used in combat for the first time.

The A2 saw even more service soon thereafter when the U.S. military sent more than a half-million personnel to the Persian Gulf in August 1990 in response to the Iraqi invasion of Kuwait. Following the decisive victory of Operation Desert Storm in 1991, the M16A2 was next used in combat when U.S. Army Rangers and soldiers from the 10th Mountain Division fought a vicious urban battle in the streets of Mogadishu, Somalia in October 1993.

With the 38.8-inch overall length of the M16A1 and the 39.5-inch overall length of the M16A2, the need for shorter and lighter versions has always been a part of the story. In late 1966, Colt introduced a version of the select-fire M16A1 with a 10-inch barrel, a two-position collapsible stock and a 4.5-inch flash/noise moderator called the XM177E1 Commando (designated GAU-5/A by the Air Force). The following year, Colt introduced a slightly modified version with a longer 11.5-inch barrel designated the XM177E2. These versions of the Commando served Army Special Operations units, Navy SEAL teams and Air Force security forces throughout the 1960s, ’70s and into the ’80s. As the transition to a product-improved rifle was taking place, Colt began developing an M16A2-based carbine in 1984. This new carbine, designated XM4, combined the compactness of the Commando series carbines with the ability to fire the new 5.56x45 mm NATO cartridge. It featured the “BURST” setting and the brass deflector of the M16A2, and was equipped with a 14.5-inch, 1:7-inch twist barrel. This barrel also included a bayonet lug—a feature missing from the Commando series—and a visible notch in the barrel forward of the front sight base to accommodate the mounting band for the M203 grenade launcher.

Although at first equipped with the signature M16 carrying handle, the XM4 was ultimately produced with a removable carry handle and a flat-top upper receiver for mounting optical sights. In September 1994, the Army standardized it as the M4 Carbine and began distributing it to combat units. Not long thereafter, Colt began to produce M4 carbines equipped with the Knight’s Armament Rail Accessory System in place of the standard forward handguards. This M4 Modular Weapons System remains in service today and accommodates the mounting of a variety of accessories, including grips, lasers and tactical lights.

When U.S. soldiers and Marines deployed to Kosovo in 1999 as part of the KFOR peacekeeping force, many of them were armed with the M4 Carbine. When the American military responded to the Sept. 11, 2001, terrorist attacks, the M4 Carbine was there and ready to fight. It saw extensive service in Afghanistan notably during Operation Anaconda in March 2002. In 2003 the M4, alongside plenty of M16A2s, armed American personnel when they returned to the deserts of Iraq. In fact, both M4s and A2s were present when soldiers of the 4th Infantry Division captured Iraqi dictator Saddam Hussein near Tikrit on Dec. 13, 2003. Following the initial success of Operation Iraqi Freedom, American forces began to combat the escalating sectarian violence of the Iraqi insurgency. During that phase of the war, yet another version of the rifle began to appear on the battlefront. The flat-top M4 Carbine proved to be so successful that a new a full length rifle with the same features was soon adopted as the M16A4 Modular Weapons System (manufactured by Colt and FN). Together with the M16A2 and the M4 Carbine, the M16A4 has been equipping the American military during the recent years of the Global War on Terror.

For 50 years the Black Rifle in its various forms has armed the American military. Today it is the rifle that is fighting the global war against terrorism, and a whole new generation of Americans has had the experience of enduring combat and facing an enemy of the United States with an M16. From the mountains of Afghanistan to the deserts of Iraq, these rifles have often been the difference between life and death for thousands of U.S. service personnel. On Sunday, March 20, 2005, 23-year old Sgt. Leigh Ann Hester of the 617th Military Police Company, Kentucky National Guard, was part of a security team for a large supply convoy south of Baghdad. When the convoy neared the town of Salman Pak, a force of approximately 50 insurgents ambushed it. Sergeant Hester and the other members of her squad immediately engaged the enemy in a fierce 25-minute firefight at close range. Armed with an M4 Carbine equipped with an M203 40 mm grenade launcher, Sgt. Hester rushed forward under fire from her vehicle to a nearby ditch. Together with her squad leader, Sgt. Hester fought her way down the length of the ditch firing her M4 Carbine at the enemy. The combat was so intense that she quickly ran out of ammunition and was forced to expose herself to the enemy’s fire again as she ran back to one of the vehicles to retrieve more. She then returned to the ditch and continued fighting until there was no opposition left. During the firefight, Sgt. Hester personally killed three insurgents with her M4 and was subsequently decorated for her actions. In addition to all of the other noteworthy points associated with the military history of the M16, it is also the arm used by the first American woman to earn the Silver Star for direct action with the enemy.

The M16 earned perhaps its greatest distinction on May 2, 2011, when a variation of the M4 Carbine was used to kill the infamous terrorist leader and September 11 mastermind Osama Bin Laden during a daring raid on his compound in Abbottabad, Pakistan.

The M16 has given 50 years of service to the American military. Although its reputation suffered during those dark days in 1966 and 1967, it has nevertheless served longer than any other rifle in U.S. military history. Soldiers, sailors, airmen, Marines and Coast Guardsmen stand watch right now, protecting the republic with this outstanding and effective firearm.