The Rock River Arms .458 SOCOM 16-inch complete upper receiver assembly allows shooters to convert an existing AR-15 lower to .458 SOCOM. The upper features a 16-inch chromoly barrel, BCG, and RRA's enhanced upper receiver with M4 feed ramps. Type: Rifle Action: Semi-Automatic Caliber: .458 SOCOM Capacity: 7 Year introduced: 2008, USA Weight: 48 oz Status: Active Intended use: Hunting, Home Defense