M16A4

The M16A4 is a 5.56×45mm NATO assault rifle in the M16 family. It was introduced by the United States in the late 1990s as the fourth major variant, designed to enhance modularity and optics compatibility while retaining the core characteristics of the platform. The rifle preserves the 20-inch government-profile barrel and the direct-gas impingement operating system of its predecessors, but replaces the carrying handle with a flat-top upper receiver to enable the mounting of optical sights. A four-rail (quad-rail) handguard allows the attachment of foregrips, lights, laser devices, and other accessories. The M16A4 uses the same fire-control system as the M16A2/A3 family, providing semi-automatic and three-round burst fire modes; safe is also available. Detachable magazines of 5.56×45mm NATO are standard, typically 20- or 30-round capacities.

Operational history and use. The M16A4 serves as a general-purpose service rifle for U.S. Army and Marine Corps units and has seen widespread use among NATO and allied forces. It has been employed in various operations and conflicts, including those associated with the Global War on Terror. Over time, many front-line forces have transitioned to lighter carbines such as the M4, but the M16A4 remains in service with some units and export operators, valued for its accuracy, optics versatility, and compatibility with standard 5.56mm ammunition.