What is a Complete AR-15 Upper Receiver? A complete AR-15 upper receiver provides one of the simplest and fastest ways to upgrade or finish an AR-15 rifle. The term refers to a pre-assembled unit that includes the upper receiver body, barrel, gas system, bolt carrier group, charging handle, handguard, forward assist, ejection port cover, and … Continue reading Buying a Complete AR-15 Upper Receiver: What to Look For