The Armalite AR-10B uses the DPMS-compatible receiver pattern rather than the proprietary AR-10A receiver, providing broader compatibility with aftermarket parts and accessories. The 20-inch barrel configuration follows the standard military rifle length, providing full ballistic performance from 7.62x51mm NATO. The B-pattern receiver has become the more popular of the two Armalite AR-10 configurations. Type: Rifle Action: Semi-Automatic Caliber: 7.62x51mm NATO Capacity: 20 Year introduced: 1995, USA Weight: 126 oz Overall length: 41.5" Status: Active Intended use: Service Rifle / Designated Marksman