Rock River Arms Coyote Carbine, Complete Upper Receiver, 300 Blackout, 16 Barrel, Smith Vortex Flash Hider, RRA 12.5 Free Float M-LOK Handguard, Anodized Finish, Black, Fits AR-15, Includes Bolt Carrier Group and Charging Handle Assembly BLK0592 Rock River Arms A4 Coyote Carbine upper comes chambered in .300 AAC / Blackout with a 16" chrome moly 1/8twist barrel. Additionally this upper includes a RRA 12.5" M-Lok compatible lightweight free float rail and a Smith Vortex flash hider (5/8-24 thread). This is a complete upper with bolt carrier group and charging handle assembly..