The Rock River Arms Complete Mid-Length A4 Upper Receiver delivers straight-wall cartridge performance in .450 Bushmaster for AR-15 lower receivers.
- Caliber: .450 Bushmaster
- Type: Complete Upper Receiver Assembly
- Compatible Lower: Mil-spec AR-15
- Barrel Length: 16 inches
- Gas System: Mid-length
- Material: Forged aluminum upper receiver
- Configuration: A4 flat-top
- Includes: 5-round magazine
- Installation: Drop-in, no gunsmithing required
