BCM BCM4 standard carbine with 16-inch M4-profile barrel, A2 flash hider, and milspec components throughout. BCM's baseline complete carbine. Type: Semi-Auto Rifle Action: Semi-Automatic Caliber: 5.56x45mm Capacity: 30 Year introduced: 2008, USA Weight: 63 oz Overall length: 32.5" Status: Active Intended use: General Purpose/Duty