Rock River Arms Tactical Carbine Complete Upper Features The Rock River Arms Tactical Carbine upper pairs a 16 inch chrome moly bull barrel with a 1:14 twist rate specifically tuned for the heavy large diameter bullets that the .458 SOCOM cartridge fires. The RRA Operator muzzle brake threaded at 5/8x32 helps manage the recoil of this big bore round so follow up shots stay controlled and on target. A low profile gas block keeps the handguard s profile slim while maintaining reliable cycling of the action under the forces generated by this cartridge. This combination of barrel contour twist rate and muzzle device makes the upper well suited to close range hunting applications where the .458 SOCOM excels. A 15 inch RRA lightweight free float handguard wraps the barrel and is compatible with M-LOK accessories giving shooters room to add lights grips or bipods without affecting barrel harmonics. The anodized black finish on the upper s A4 receiver resists wear while matching most AR-15 lower builds for a clean uniform look. Rock River Arms includes a complete bolt carrier group and charging handle assembly with the upper so it can be dropped onto a compatible AR-15 lower with minimal additional parts needed. For builders looking to add a hard hitting big bore option to their AR-15 platform this Tactical Carbine upper is available for sale at GrabAGun. Rock River Arms Tactical Carbine Complete Upper Specifications Manufacturer: Rock River Arms Model: Tactical Carbine Complete Upper Type: Complete Upper Receiver Caliber: .458 SOCOM Barrel Length: 16 Barrel Material: Chrome Moly Muzzle Device: RRA Operator Muzzle Brake Handguard: 15 RRA Free Float M-LOK Finish: Anodized Color: Black Compatible Hosts: AR-15 Includes: Bolt Carrier Group and Charging Handle Assembly Available At: GrabAGun