FN USA FN 15 Military Collector Series M16A4 Complete Upper Receiver Assembly 5.56mm 20" Barrel

The FN USA FN 15 Military Collector Series M16A4 Complete Upper Receiver Assembly 5.56mm 20" Barrel offers shooters an authentic reproduction of the iconic service rifle utilized by the U.S. military. This complete upper is engineered for enthusiasts and collectors who demand the same level of reliability and craftsmanship found in frontline combat hardware. By adhering to the original technical data package, FN ensures that this assembly bridges the gap between historical significance and modern performance requirements. It serves as a foundational component for those building a clone-correct rifle or seeking the ballistic advantages of a full-length barrel system.

At the core of this system is a 20-inch chrome-lined barrel chambered in 5.56x45mm NATO, providing the increased muzzle velocity necessary for superior terminal ballistics at extended ranges. The assembly features the classic M16A4 configuration, including a fixed front sight base and a flat-top receiver designed for the mounting of period-correct optics or detachable carry handles. Precision-machined from high-grade materials, the bolt carrier group and receiver are built to withstand high-volume fire while maintaining consistent headspace and cycling reliability. The integrated rail system allows for the secure attachment of tactical lights, vertical grips, and other mission-essential accessories without compromising structural integrity.

This upper receiver assembly is an ideal choice for marksmen who prioritize the stability and extended sight radius of a traditional rifle-length gas system, which significantly reduces felt recoil compared to shorter carbine variants. Installation is straightforward on any standard AR-15 pattern lower receiver, making it a versatile upgrade for duty use, competition, or range training. Its heavy-duty construction ensures it remains a dependable workhorse under harsh environmental conditions. Whether you are completing a military-inspired build or looking for a durable long-range solution, this FN USA upper delivers proven battlefield performance to the civilian market.