Rock River Arms | Mid A4 Upper | .450 Bushmaster | 16″

Rock River Arms supplies this complete mid-length A4 upper chambered in .450 Bushmaster, built on a 16″ chrome-moly barrel with a 1:24 twist for consistent stabilization of appropriate projectiles. The assembly ships ready with a bolt carrier group, charging handle, and an RRA Operator Brake (5/8-32 thread), and includes a 13″ M-LOK lightweight free-float rail for accessory mounting. Intended for integration with AR-15 lower receivers, this upper suits applications such as medium-bore brush hunting and precision short- to mid-range shooting scenarios.

Product Specifications

• The manufacturer is Rock River Arms.
• The product is a complete upper receiver described as Tactical Carbine.
• The unit is chambered in .450 Bushmaster.
• The barrel measures 16″ and is constructed from chrome moly with a 1:24 twist.
• The gas system length is mid-length.
• The handguard is a 13″ M-LOK lightweight free-float rail.
• The muzzle device is an RRA Operator Brake (5/8-32 thread).
• The assembly includes a bolt carrier group and charging handle.
• The finish is Anodized and the color is Black.
• The package ships with one 5-round magazine for initial use.
• The upper is designed to fit AR-15 lowers.
• The product category is Complete Upper Receivers.
• The stated capacity is 5 rounds.
• The listed accessories include 1 Magazine.
• The UPC for this product is 842834125548.

Configured to integrate directly with standard AR-15 lowers, this Rock River Arms complete upper offers a purpose-driven .450 Bushmaster package with a balance of handling and capability. The free-float 13″ M-LOK rail provides room for optics and accessories while the 16″ chrome-moly barrel and operator brake deliver consistent performance for field work and deliberate precision shooting. For users seeking a turnkey mid-length upper in .450 Bushmaster, this assembly combines core components into a single, install-ready unit.