Rock River Arms A4 mid-length upper comes chambered in .450 Bushmaster with a 16" chrome moly 1/24 twist barrel. Additionally this upper includes a RRA 13" M-Lok compatible lightweight free float rail and a RRA Operator Brake (5/8-32 thread). This is a complete upper with bolt carrier group, charging handle assembly and a 5 round magazine.

Features :

• .450 Bushmaster
• 16 Inch Chrome Moly, 1:24 Twist
• RRA Operator Brake, 5/8-32 Thread
• Low Profile Gas Block, Mid-Length Gas System
• RRA 13 Inch Extended Lightweight Free Float Rail
• Bolt Carrier Group, Charging Handle Assembly
• (1) Magazine, (5) Rounds