AeroPrecision167528120
M4E1 300Blk Assembled Upper 8''Bbl Threaded W/Rm7.3'' Hg Fde$610.20
Availability: In Stock
Current Stock: Out of stock
The Aero Precision M4E1 300 Blackout assembled upper with 10-inch barrel and threaded muzzle is a complete, ready-to-run upper receiver built for shooters who want a compact, capable platform for subsonic shooting, close-quarters hunting, or specialized tactical work. This upper comes fully assembled—just pair it with a lower receiver, bolt carrier group, and charging handle to complete your build. The 10-inch barrel length hits the sweet spot for 300 Blackout: short enough for maneuverability and hearing protection when running subsonic ammo, long enough to deliver reliable performance in a modern sporting rifle.
At the heart of this upper is Aero Precision's ATLAS R-ONE handguard, engineered to balance weight savings with mounting versatility. The R-ONE uses Aero's proprietary ATLAS attachment system—a proven platform that's slim and lightweight while maintaining the rigidity and strength Aero shooters expect. The full-length top picatinny rail accepts optics, backup sights, and accessories; quick-disconnect sling mounts at 3, 6, and 9 o'clock positions let you configure the rifle your way. The handguard is cut for low-profile gas blocks, and its dimensions (1.3" ID, 1.5" OD) keep the overall package compact without sacrificing real estate for lights, lasers, or other tactical gear.
The barrel itself is 4150 chrome moly vanadium with a QPQ corrosion-resistant finish inside and out—tough steel built to last through thousands of rounds. It's threaded 5/8x24 at the muzzle, compatible with most suppressors, flash hiders, and muzzle devices (the included A2 flash hider is not pinned or welded, so you can swap it easily). The gas system is rifle-length on a .750 low-profile gas block, tuned for reliable cycling with 300 Blackout's subsonic and supersonic loads. The M4E1 upper receiver features M4 feedramps, enhanced forging with a billet appearance, laser-engraved T-marks for reference, and includes the port door and forward assist. This upper does not include a bolt carrier group or charging handle—those are your choice to round out the build.
Whether you're building a short-range hunting rifle, a suppressed subsonic platform, or a compact home-defense upper, this Aero Precision assembly delivers the precision and reliability you need from a name that's earned trust across the shooting community.
| Brand | Aero Precision |
| Caliber | .300 Blackout |
| Barrel Length | 10 inches |
| Barrel Material | 4150 Chrome Moly Vanadium |
| Barrel Finish | QPQ (corrosion-resistant inside and out) |
| Muzzle Thread | 5/8x24 |
| Gas Port Diameter | .0935 inches |
| Gas System Length | Rifle length |
| Gas Block | Low-profile .750 |
| Barrel Weight | 21 oz |
| Upper Receiver Type | M4E1 (enhanced forging) |
| Feedramp Style | M4 |
| Handguard | ATLAS R-ONE |
| Handguard ID | 1.3 inches |
| Handguard OD | 1.5 inches |
| Top Rail | Full-length picatinny |
| Sling Mounts | QD at 3, 6, and 9 o'clock |
| Included Muzzle Device | A2 Flash Hider (not pinned/welded) |
| Condition | Fully assembled |
| Not Included | Bolt carrier group, charging handle |
This is a fully assembled upper receiver, but it does not include a bolt carrier group (BCG) or charging handle. You'll need to source those separately to complete the upper and make it functional.
Yes. The A2 flash hider that comes with this upper is not pinned or welded to the barrel, so you can remove it easily. The muzzle is threaded 5/8x24, which is standard for 300 Blackout suppressors and muzzle devices.
The ATLAS R-ONE uses Aero Precision's proprietary ATLAS attachment system, which is designed to be lighter and slimmer than traditional picatinny tube handguards while maintaining rigidity and strength. It features a full-length top picatinny rail, quick-disconnect sling mounts at 3, 6, and 9 o'clock, and is compatible with low-profile gas blocks.
Aero Precision offers 300 Blackout barrels in 8-inch, 10-inch, and 16-inch lengths. This specific product includes the 10-inch barrel.
Yes. The M4E1 upper receiver is compatible with standard mil-spec AR15 lower receivers. It features .250 takedown pin holes and M4 feedramps for reliable feeding.
SKU: 167528127 • Weight: 4oz
Availability: In Stock
Current Stock: Out of stock
The Aero Precision M4E1 300 Blackout assembled upper with 10-inch barrel and threaded muzzle is a complete, ready-to-run upper receiver built for shooters who want a compact, capable platform for subsonic shooting, close-quarters hunting, or specialized tactical work. This upper comes fully assembled—just pair it with a lower receiver, bolt carrier group, and charging handle to complete your build. The 10-inch barrel length hits the sweet spot for 300 Blackout: short enough for maneuverability and hearing protection when running subsonic ammo, long enough to deliver reliable performance in a modern sporting rifle.
At the heart of this upper is Aero Precision's ATLAS R-ONE handguard, engineered to balance weight savings with mounting versatility. The R-ONE uses Aero's proprietary ATLAS attachment system—a proven platform that's slim and lightweight while maintaining the rigidity and strength Aero shooters expect. The full-length top picatinny rail accepts optics, backup sights, and accessories; quick-disconnect sling mounts at 3, 6, and 9 o'clock positions let you configure the rifle your way. The handguard is cut for low-profile gas blocks, and its dimensions (1.3" ID, 1.5" OD) keep the overall package compact without sacrificing real estate for lights, lasers, or other tactical gear.
The barrel itself is 4150 chrome moly vanadium with a QPQ corrosion-resistant finish inside and out—tough steel built to last through thousands of rounds. It's threaded 5/8x24 at the muzzle, compatible with most suppressors, flash hiders, and muzzle devices (the included A2 flash hider is not pinned or welded, so you can swap it easily). The gas system is rifle-length on a .750 low-profile gas block, tuned for reliable cycling with 300 Blackout's subsonic and supersonic loads. The M4E1 upper receiver features M4 feedramps, enhanced forging with a billet appearance, laser-engraved T-marks for reference, and includes the port door and forward assist. This upper does not include a bolt carrier group or charging handle—those are your choice to round out the build.
Whether you're building a short-range hunting rifle, a suppressed subsonic platform, or a compact home-defense upper, this Aero Precision assembly delivers the precision and reliability you need from a name that's earned trust across the shooting community.
| Brand | Aero Precision |
| Caliber | .300 Blackout |
| Barrel Length | 10 inches |
| Barrel Material | 4150 Chrome Moly Vanadium |
| Barrel Finish | QPQ (corrosion-resistant inside and out) |
| Muzzle Thread | 5/8x24 |
| Gas Port Diameter | .0935 inches |
| Gas System Length | Rifle length |
| Gas Block | Low-profile .750 |
| Barrel Weight | 21 oz |
| Upper Receiver Type | M4E1 (enhanced forging) |
| Feedramp Style | M4 |
| Handguard | ATLAS R-ONE |
| Handguard ID | 1.3 inches |
| Handguard OD | 1.5 inches |
| Top Rail | Full-length picatinny |
| Sling Mounts | QD at 3, 6, and 9 o'clock |
| Included Muzzle Device | A2 Flash Hider (not pinned/welded) |
| Condition | Fully assembled |
| Not Included | Bolt carrier group, charging handle |
This is a fully assembled upper receiver, but it does not include a bolt carrier group (BCG) or charging handle. You'll need to source those separately to complete the upper and make it functional.
Yes. The A2 flash hider that comes with this upper is not pinned or welded to the barrel, so you can remove it easily. The muzzle is threaded 5/8x24, which is standard for 300 Blackout suppressors and muzzle devices.
The ATLAS R-ONE uses Aero Precision's proprietary ATLAS attachment system, which is designed to be lighter and slimmer than traditional picatinny tube handguards while maintaining rigidity and strength. It features a full-length top picatinny rail, quick-disconnect sling mounts at 3, 6, and 9 o'clock, and is compatible with low-profile gas blocks.
Aero Precision offers 300 Blackout barrels in 8-inch, 10-inch, and 16-inch lengths. This specific product includes the 10-inch barrel.
Yes. The M4E1 upper receiver is compatible with standard mil-spec AR15 lower receivers. It features .250 takedown pin holes and M4 feedramps for reliable feeding.
SKU: 167528127 • Weight: 4oz