Rock River Arms' dedicated .458 SOCOM build — a AR-15 lower-pattern rifle chambered in .458 SOCOM, the large-bore cartridge designed by Tony Rumore and Marty ter Weeme for special operations. Uses a standard AR-15 lower with a dedicated .458 SOCOM upper. Delivers rifle-caliber terminal performance from a suppressor-optimized big-bore round. Type: Rifle Action: Semi-Automatic Caliber: .458 SOCOM Capacity: 10 Year introduced: 2008, United States Weight: 108.8 oz Overall length: 34.5" Status: Active Intended use: Hunting, Home Defense