Bushmaster 0040008BLK M4 Patrolman's Upper 5.56x45mm NATO 20" Black Rec/Barrel for AR-15

The Bushmaster 0040008BLK M4 Patrolman's Upper 5.56x45mm NATO 20" Black Rec/Barrel for AR-15 is a direct-impingement upper receiver assembly purpose-built for patrol and duty applications where reliability and accuracy matter. This complete upper is designed for officers and shooters who demand a versatile platform capable of intermediate engagement ranges while maintaining the ergonomic familiarity of the M4/AR-15 platform. The 20-inch barrel configuration balances velocity, sight radius, and handling for law enforcement, security, and civilian defensive use.

Chambered in 5.56x45mm NATO, this upper receiver assembly delivers the ballistic performance and ammunition commonality essential to duty and patrol environments. The 20-inch barrel maximizes muzzle velocity and extends effective range compared to carbine-length alternatives, while the flat-top Picatinny rail system provides unlimited mounting flexibility for optics, iron sights, and accessories. Bushmaster's proven manufacturing standards ensure consistent chamber tolerances and reliable feeding, and the black anodized finish resists corrosion during extended field use and adverse weather conditions. The direct-impingement gas system is time-tested across millions of rounds in military and law enforcement service.

This upper assembly is fully compatible with any AR-15 compatible lower receiver, making it an ideal upgrade or replacement component for officers building or maintaining duty rifles. Patrol units, security details, and prepared civilians benefit from the extended barrel length and velocity advantage without sacrificing the modularity that defines the AR platform. Weighing 4.64 pounds, the upper maintains a manageable profile suitable for vehicle storage, building entry, and sustained marksmanship from supported and unsupported positions. Installation requires only a pivot pin and takedown pin connection to a compatible lower receiver—no gunsmith work necessary.