Rock River Arms Completed Upper Receiver A4 9MM Luger 4.5 Inch Barrel 1-10 Twist 1/2-36 Thread Free-Float Handguard Vortex Flash Hider Black
All Rock River Arms upper receivers
Click to see full view
Rock River Arms
Overview
The Rock River Arms Completed Upper Receiver A4 is designed for the AR-9 platform, featuring a 4.5-inch barrel specifically chambered in 9mm. With a 1:10 twist rate, this upper provides good stability and accuracy for various 9mm ammunition types, while the 1/2x36 thread pitch allows for easy attachment of muzzle devices. This setup is commonly utilized in shorter, more compact builds perfect for close-quarters engagements or competitive shooting scenarios.
Specifications
Rock River Arms Completed Upper Receiver A4 9MM Luger 4.5 Inch Barrel 1-10 Twist 1/2-36 Thread Free-Float Handguard Vortex Flash Hider Black
Available Merchants(1)
Prices checked
Stock Alert
Build history on GunPartPicker
Builders on GunPartPicker first added the Rock River Arms Completed Upper Receiver A4 9MM Luger 4.5 Inch Barrel 1-10 Twist 1/2-36 Thread Free-Float Handguard Vortex Flash Hider Black to a build in March 2026.
Today the one retailer we track is out of stock. Listed prices start at $569.99 at Optics Planet for when it comes back.
Updated · from real builds on GunPartPicker · Prices checked · refreshed daily across 37 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
Popular alongside upper receivers on GunPartPicker
Aero Precision M4E1 Complete Lower Receiver W/MOE SL Grip & SL-S Carbine Stock
Aero Precision AR-15 Breach Charging Handle Ambidextrous Small Levers
Geissele Automatics AR-15 SSA-E X Lightning Bow Trigger
Bravo Company M16 Bolt Carrier Group Black
Magpul AFG-2 Angled Fore Grip - Black
Magpul AR-15 MOE Stock Collapsible Mil-Spec Black
No reviews yet. Be the first to review this product!