Rock River Arms Completed Upper Receiver A4 .450 Bushmaster 20 Inch Barrel 1-24 Twist 5/8-32 Thread Free-Float Handguard Brake Black
Click to see full view
Rock River Arms
Overview
The Rock River Arms Completed Upper Receiver A4 is a fully assembled upper designed for the AR-15 platform, featuring a 20-inch barrel specifically chambered in .450 Bushmaster. This configuration provides a robust option for those seeking to utilize the .450 caliber, which is known for its stopping power and versatility in various shooting applications. Commonly, this upper receiver appears in builds tailored for hunting or tactical use, where the added barrel length contributes to improved accuracy and performance.
Specifications
Rock River Arms Completed Upper Receiver A4 .450 Bushmaster 20 Inch Barrel 1-24 Twist 5/8-32 Thread Free-Float Handguard Brake Black
Build history on GunPartPicker
Builders have been adding the Rock River Arms Completed Upper Receiver A4 .450 Bushmaster 20 Inch Barrel 1-24 Twist 5/8-32 Thread Free-Float Handguard Brake Black to their builds on GunPartPicker since March 2026. All time, it ranks #457 of the 1,630 upper receivers builders have added.
It was in stock most days in August 2026, but today the one retailer we track is out of stock. Prices barely moved in August 2026, holding around $649.99, so there haven't been real sales lately. Listed prices start at $649.99 at Optics Planet for when it comes back.
Updated · from real builds on GunPartPicker · Prices checked · refreshed daily across 35 retailers
Not sure which upper receiver to pick?
We ranked every upper receiver by how often it shows up in real builds on GunPartPicker.
Read the guide: Most Popular AR-15 Upper Receivers →Check it against the live catalog:
Frequently Built With
The part most often added in each category by the 3 builds that include this one
WMD Guns M16/AR-15 Bolt Carrier Group BCG .450 BM NIB-X Nickel
Rise Armament Advanced Performance Trigger, Red - RA-535-RED-ARP
AR-15 Mike-45 Complete Billet Rifle Lower Receiver
Timber Creek Outdoors AR-15 Takedown Pin Set - Red
Rise Armament AR-15 Magazine Release Button - Rise Red
Hogue AR-15 OverMolded Pistol Grip - Beaver Tail - No Finger Grooves - Black
No reviews yet. Be the first to review this product!