AeroPrecision167528121
M4E1 300Blk Assembled Upper 16''Bbl Threaded W/Rm15'' Hg Fde$534.99
Availability: In Stock
Current Stock: Out of stock
The Aero Precision M4E1 300 Blackout assembled upper receiver pairs a precision-forged upper with a 16-inch .300 BLK barrel and the company's slim-profile ATLAS R-ONE handguard—a complete, ready-to-run platform for hunters and shooters building a subsonic or supersonic 300 Blackout rifle. This upper comes fully assembled with a low-profile gas block, threaded muzzle, and all the internal goodies installed, so you're ready to mate it to a lower receiver, bolt carrier group, and charging handle to get on target.
The 16-inch barrel is built from 4150 Chrome Moly Vanadium steel with a 1-in-7 twist, optimized for standard and heavier 300 Blackout loads. The muzzle is threaded 5/8x24 and finished with an A2 flash hider (not pinned or welded, so you can swap it for a suppressor or muzzle brake if needed). The QPQ corrosion-resistant finish protects the barrel inside and out. The gas system is set to pistol length, pairing with the low-profile gas block for a clean look under the handguard.
The M4E1 upper receiver itself features an enhanced forging that delivers a billet aesthetic without the weight penalty, plus refined picatinny rails that mesh seamlessly with Aero's Extended Series handguards and accessories. It includes M4 feedramps, port door, forward assist, and laser-etched T-marks. The ATLAS R-ONE handguard spans 15 inches, keeping weight minimal while offering full top rail real estate and quick-detach sling mounts at 3, 6, and 9 o'clock. Its proprietary ATLAS mounting system is rock-solid and maintains a slim 1.3-inch inner diameter—compatible with standard mil-spec AR barrels and low-profile gas blocks.
This is an assembled upper—no BCG or charging handle included—so you'll need those components to complete your build. If you run suppressors or subsonic ammo, the 300 Blackout platform in a 16-inch format strikes a practical balance between velocity and package size.
| Product Type | Assembled Upper Receiver |
| Brand | Aero Precision |
| Caliber | .300 Blackout |
| Barrel Length | 16 inches |
| Barrel Material | 4150 Chrome Moly Vanadium |
| Barrel Twist | 1 in 7 |
| Muzzle Threading | 5/8x24 (threaded, A2 flash hider included, not pinned/welded) |
| Finish | QPQ corrosion-resistant (barrel and internals) |
| Gas System | Pistol length with low-profile gas block (.750 bore) |
| Upper Receiver | M4E1 Enhanced Forged with M4 feedramps |
| Handguard | ATLAS R-ONE (15-inch) |
| Handguard Inner/Outer Diameter | 1.3" ID / 1.5" OD |
| Handguard Sling Mounts | QD sockets at 3, 6, and 9 o'clock |
| Included | Assembled upper receiver, ATLAS R-ONE handguard, barrel, low-profile gas block, port door, forward assist, A2 flash hider |
| Not Included | Bolt carrier group (BCG), charging handle |
This is an assembled upper receiver only. You'll need a lower receiver, a bolt carrier group (BCG), and a charging handle to finish the build. Once those are paired with this upper, you'll have a complete, functional rifle.
No. The A2 flash hider that ships with this upper is removable, not pinned or welded. You can swap it out for a suppressor or other muzzle device that fits the 5/8x24 threading if desired.
The ATLAS R-ONE handguard (15 inches long) is included. It features a full top picatinny rail for optics and accessories, plus quick-detach sling mounts at the 3, 6, and 9 o'clock positions.
Yes, this M4E1 upper is compatible with standard mil-spec AR15 lower receivers and bolt carrier groups. You'll need to source your own BCG and charging handle to complete the build.
SKU: 167528123 • Weight: 5oz
Availability: In Stock
Current Stock: Out of stock
The Aero Precision M4E1 300 Blackout assembled upper receiver pairs a precision-forged upper with a 16-inch .300 BLK barrel and the company's slim-profile ATLAS R-ONE handguard—a complete, ready-to-run platform for hunters and shooters building a subsonic or supersonic 300 Blackout rifle. This upper comes fully assembled with a low-profile gas block, threaded muzzle, and all the internal goodies installed, so you're ready to mate it to a lower receiver, bolt carrier group, and charging handle to get on target.
The 16-inch barrel is built from 4150 Chrome Moly Vanadium steel with a 1-in-7 twist, optimized for standard and heavier 300 Blackout loads. The muzzle is threaded 5/8x24 and finished with an A2 flash hider (not pinned or welded, so you can swap it for a suppressor or muzzle brake if needed). The QPQ corrosion-resistant finish protects the barrel inside and out. The gas system is set to pistol length, pairing with the low-profile gas block for a clean look under the handguard.
The M4E1 upper receiver itself features an enhanced forging that delivers a billet aesthetic without the weight penalty, plus refined picatinny rails that mesh seamlessly with Aero's Extended Series handguards and accessories. It includes M4 feedramps, port door, forward assist, and laser-etched T-marks. The ATLAS R-ONE handguard spans 15 inches, keeping weight minimal while offering full top rail real estate and quick-detach sling mounts at 3, 6, and 9 o'clock. Its proprietary ATLAS mounting system is rock-solid and maintains a slim 1.3-inch inner diameter—compatible with standard mil-spec AR barrels and low-profile gas blocks.
This is an assembled upper—no BCG or charging handle included—so you'll need those components to complete your build. If you run suppressors or subsonic ammo, the 300 Blackout platform in a 16-inch format strikes a practical balance between velocity and package size.
| Product Type | Assembled Upper Receiver |
| Brand | Aero Precision |
| Caliber | .300 Blackout |
| Barrel Length | 16 inches |
| Barrel Material | 4150 Chrome Moly Vanadium |
| Barrel Twist | 1 in 7 |
| Muzzle Threading | 5/8x24 (threaded, A2 flash hider included, not pinned/welded) |
| Finish | QPQ corrosion-resistant (barrel and internals) |
| Gas System | Pistol length with low-profile gas block (.750 bore) |
| Upper Receiver | M4E1 Enhanced Forged with M4 feedramps |
| Handguard | ATLAS R-ONE (15-inch) |
| Handguard Inner/Outer Diameter | 1.3" ID / 1.5" OD |
| Handguard Sling Mounts | QD sockets at 3, 6, and 9 o'clock |
| Included | Assembled upper receiver, ATLAS R-ONE handguard, barrel, low-profile gas block, port door, forward assist, A2 flash hider |
| Not Included | Bolt carrier group (BCG), charging handle |
This is an assembled upper receiver only. You'll need a lower receiver, a bolt carrier group (BCG), and a charging handle to finish the build. Once those are paired with this upper, you'll have a complete, functional rifle.
No. The A2 flash hider that ships with this upper is removable, not pinned or welded. You can swap it out for a suppressor or other muzzle device that fits the 5/8x24 threading if desired.
The ATLAS R-ONE handguard (15 inches long) is included. It features a full top picatinny rail for optics and accessories, plus quick-detach sling mounts at the 3, 6, and 9 o'clock positions.
Yes, this M4E1 upper is compatible with standard mil-spec AR15 lower receivers and bolt carrier groups. You'll need to source your own BCG and charging handle to complete the build.
SKU: 167528123 • Weight: 5oz