Fn Upper 556 20" Complete

The FN Upper 556 20" Complete is a precision-engineered upper receiver assembly purpose-built for the AR-15 platform. This 20-inch configuration delivers extended sight radius and optimized velocity for the 5.56 NATO cartridge, making it the standard choice for marksmen who demand accuracy at distance. At 6.88 lbs, the completed upper balances controllability with the mass-forward design preferred in tactical and competition shooting environments.

The 20-inch barrel length is the proven baseline for 5.56 performance, consistently achieving muzzle velocities in the 2,800–2,900 fps range depending on ammunition selection—a critical factor for terminal ballistics and trajectory stability beyond 300 meters. Complete upper assemblies eliminate the complexity of sourcing matched components; this unit arrives as a bolt-together assembly ready to mate with a compatible lower receiver. The dimensions (31.5" overall length with handguard) confirm the full-length profile shooters expect from a rifle-class configuration, not a carbine variant.

This upper is suited for law enforcement marksmen requiring precision duty rifles, competitive shooters in 3-Gun or precision rifle matches, and civilians building AR-15 platforms for target practice or home defense. The 20-inch barrel works equally well from a bench, prone position, or supported fire in tactical scenarios where accuracy takes priority over compactness. Operators selecting a complete upper avoid the risk of incompatible components and gain confidence in factory-tested assembly standards.