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Brownells
The Brownells BRN-15 5.56mm 16" upper receiver is a ready-to-assemble upper for builders looking to put together a reliable AR-pattern rifle without starting from scratch. This forged Mil-Spec upper comes complete with a nitride-finished 4150 CMV barrel, M4 feed ramps, ejection port cover, and forward assist—everything you need except the bolt carrier group and charging handle. It's American-made from the ground up, built on proven 7075-T6 aluminum that's hardcoat anodized to resist corrosion and wear.
The 16-inch barrel is chambered in 5.56x45mm NATO with a 1-7 twist rate and features a dimpled gas block shoulder for secure, repeatable seating. A2 flash hider comes pinned and ready (note: the lightweight version uses a lock nut for easier removal). The handguard is where Brownells added smart details—an M-LOK platform extends generously forward, with anti-rotation tabs that lock it to the upper receiver to eliminate any shift or cant relative to the Picatinny rail. Dual clamping screws pass through a properly torqued barrel nut, and vented design lets heat escape during shooting or training. Whether you're building your first AR or your fifth, this upper gives you a solid foundation without compromise.
All barrels are stress-relieved and marked with caliber and twist specs. The 1/2-28 muzzle threads accept standard AR suppressors and muzzle devices. Simply pair this upper with your choice of lower receiver, bolt carrier group, and charging handle to complete the build.
| Caliber | 5.56x45mm NATO |
| Barrel Length | 16 inches |
| Barrel Material | 4150 Chrome Moly Vanadium |
| Barrel Twist | 1-7 |
| Barrel Finish | Nitride |
| Gas Block Diameter | .625 inch |
| Muzzle Thread | 1/2-28 |
| Muzzle Device | A2 Flash Hider (pinned) |
| Upper Receiver Type | Forged Mil-Spec |
| Upper Receiver Material | 7075-T6 Aluminum |
| Upper Receiver Finish | Hardcoat Anodized |
| Feed Ramps | M4 (in upper and barrel extension) |
| Handguard Type | M-LOK |
| Country of Origin | USA |
This upper comes assembled and ready to attach to a lower receiver, but you'll need to source a bolt carrier group and charging handle separately. Once you have those three components (upper, lower, BCG, and charging handle), your AR will be complete and functional.
Yes. The barrel is threaded 1/2-28 and comes with an A2 flash hider installed. You can unscrew the flash hider (note: the lightweight version uses a lock nut that must be secured with a wrench before removal) and install any standard 1/2-28 suppressor or muzzle device.
The barrel features a .625-inch gas block dimple. This is the standard rifle-length gas block diameter and accepts common .625" gas blocks for your build.
Yes, this is a Mil-Spec forged upper receiver with M4 feed ramps, designed to work with standard AR-15 lower receivers. It will mate with any mil-spec or commercial lower.
Brownells
The Brownells BRN-15 5.56mm 16" upper receiver is a ready-to-assemble upper for builders looking to put together a reliable AR-pattern rifle without starting from scratch. This forged Mil-Spec upper comes complete with a nitride-finished 4150 CMV barrel, M4 feed ramps, ejection port cover, and forward assist—everything you need except the bolt carrier group and charging handle. It's American-made from the ground up, built on proven 7075-T6 aluminum that's hardcoat anodized to resist corrosion and wear.
The 16-inch barrel is chambered in 5.56x45mm NATO with a 1-7 twist rate and features a dimpled gas block shoulder for secure, repeatable seating. A2 flash hider comes pinned and ready (note: the lightweight version uses a lock nut for easier removal). The handguard is where Brownells added smart details—an M-LOK platform extends generously forward, with anti-rotation tabs that lock it to the upper receiver to eliminate any shift or cant relative to the Picatinny rail. Dual clamping screws pass through a properly torqued barrel nut, and vented design lets heat escape during shooting or training. Whether you're building your first AR or your fifth, this upper gives you a solid foundation without compromise.
All barrels are stress-relieved and marked with caliber and twist specs. The 1/2-28 muzzle threads accept standard AR suppressors and muzzle devices. Simply pair this upper with your choice of lower receiver, bolt carrier group, and charging handle to complete the build.
| Caliber | 5.56x45mm NATO |
| Barrel Length | 16 inches |
| Barrel Material | 4150 Chrome Moly Vanadium |
| Barrel Twist | 1-7 |
| Barrel Finish | Nitride |
| Gas Block Diameter | .625 inch |
| Muzzle Thread | 1/2-28 |
| Muzzle Device | A2 Flash Hider (pinned) |
| Upper Receiver Type | Forged Mil-Spec |
| Upper Receiver Material | 7075-T6 Aluminum |
| Upper Receiver Finish | Hardcoat Anodized |
| Feed Ramps | M4 (in upper and barrel extension) |
| Handguard Type | M-LOK |
| Country of Origin | USA |
This upper comes assembled and ready to attach to a lower receiver, but you'll need to source a bolt carrier group and charging handle separately. Once you have those three components (upper, lower, BCG, and charging handle), your AR will be complete and functional.
Yes. The barrel is threaded 1/2-28 and comes with an A2 flash hider installed. You can unscrew the flash hider (note: the lightweight version uses a lock nut that must be secured with a wrench before removal) and install any standard 1/2-28 suppressor or muzzle device.
The barrel features a .625-inch gas block dimple. This is the standard rifle-length gas block diameter and accepts common .625" gas blocks for your build.
Yes, this is a Mil-Spec forged upper receiver with M4 feed ramps, designed to work with standard AR-15 lower receivers. It will mate with any mil-spec or commercial lower.
