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AeroPrecision
The Aero Precision M4E1 5.56 NATO assembled upper receiver is a ready-to-mount upper for AR-15 builders who want quality from a trusted maker without overpaying for billet aesthetics. This 16" carbine comes fully assembled with barrel, handguard, and rail system already installed—you just need to add your bolt carrier group and charging handle, which most shooters replace anyway. It splits the difference between forged and billet receivers: you get the custom look and ergonomics of a precision-machined design with the legendary mil-spec compatibility and durability that makes AR-15s so modular.
Built from 7075 T6 forged aluminum and hardcoat anodized to Mil 8625 Type 3 Class 2 spec, the M4E1 receiver is as tough as they come. The 4150 chrome-moly-vanadium barrel wears a black QPQ finish and is rifled 1-7" for reliable cycling of 5.56 NATO and .223 Remington ammunition. A carbine-length gas system with low-profile gas block keeps the platform running smooth whether you're running suppressed or unsuppressed. The A2-style flash suppressor is pinned and ready to go.
Mounted to the receiver is Aero's Gen 2 Enhanced M-LOK handguard—a solid, monolithic rail platform with a full-length Picatinny top rail running rear to muzzle. M-LOK slots around the 3, 6, and 9 o'clock positions accept the included QD sling swivel sockets and any standard M-LOK accessory you want to run. Milled texture on the flats gives you better grip and a finished look. The handguard's 1.78" inner diameter clears most muzzle devices and standard 1.5" suppressors.
If you're building a duty rifle, match gun, or hunting carbine and want a no-nonsense upper that does the job right without the premium markup, the M4E1 delivers. Choose from 9" or 15" handguard length depending on your build.
| Caliber | 5.56 NATO (.223 Remington compatible) |
| Barrel Length | 16" |
| Barrel Material | 4150 Chrome-Moly-Vanadium |
| Barrel Twist | 1-7" |
| Barrel Finish | Black QPQ |
| Receiver Material | 7075 T6 Forged Aluminum |
| Receiver Finish | Mil 8625 Type 3 Class 2 Hardcoat Anodize |
| Gas System | Carbine-length with low-profile gas block |
| Handguard Type | Gen 2 Enhanced M-LOK monolithic rail |
| Handguard OAL Options | 9" or 15" |
| Handguard Inner Diameter | 1.78" |
| Top Rail | Full-length Picatinny |
| Muzzle Device | A2-style flash suppressor |
| Pivot/Takedown Pins | .250" diameter |
| Included Components | Assembled upper receiver, barrel, handguard, gas block, ejection port cover, forward assist, flash suppressor |
| Not Included | Bolt carrier group, charging handle |
The M4E1 comes fully assembled except for the bolt carrier group and charging handle. You'll need to source those separately—they're the two components most builders replace anyway, so having a choice is a feature. Once you drop in a BCG and charging handle, it'll be ready to mate with a lower receiver.
Yes. The barrel is chambered for 5.56 NATO and will reliably cycle both 5.56 NATO and .223 Remington ammunition.
The handguard has a 1.78" inner diameter that accommodates most muzzle devices and standard 1.5" suppressors. Verify the specific suppressor's dimensions if you're running something unusual, but standard suppressors will fit without issue.
The M4E1 comes with either a 9" or 15" M-LOK handguard. Shorter handguards suit shorter overall length builds or closer-quarters use, while longer handguards give you more rail space for accessories and a more traditional carbine profile. Both are monolithic and provide the same quality rail system—it's up to your intended use and preference.
AeroPrecision
The Aero Precision M4E1 5.56 NATO assembled upper receiver is a ready-to-mount upper for AR-15 builders who want quality from a trusted maker without overpaying for billet aesthetics. This 16" carbine comes fully assembled with barrel, handguard, and rail system already installed—you just need to add your bolt carrier group and charging handle, which most shooters replace anyway. It splits the difference between forged and billet receivers: you get the custom look and ergonomics of a precision-machined design with the legendary mil-spec compatibility and durability that makes AR-15s so modular.
Built from 7075 T6 forged aluminum and hardcoat anodized to Mil 8625 Type 3 Class 2 spec, the M4E1 receiver is as tough as they come. The 4150 chrome-moly-vanadium barrel wears a black QPQ finish and is rifled 1-7" for reliable cycling of 5.56 NATO and .223 Remington ammunition. A carbine-length gas system with low-profile gas block keeps the platform running smooth whether you're running suppressed or unsuppressed. The A2-style flash suppressor is pinned and ready to go.
Mounted to the receiver is Aero's Gen 2 Enhanced M-LOK handguard—a solid, monolithic rail platform with a full-length Picatinny top rail running rear to muzzle. M-LOK slots around the 3, 6, and 9 o'clock positions accept the included QD sling swivel sockets and any standard M-LOK accessory you want to run. Milled texture on the flats gives you better grip and a finished look. The handguard's 1.78" inner diameter clears most muzzle devices and standard 1.5" suppressors.
If you're building a duty rifle, match gun, or hunting carbine and want a no-nonsense upper that does the job right without the premium markup, the M4E1 delivers. Choose from 9" or 15" handguard length depending on your build.
| Caliber | 5.56 NATO (.223 Remington compatible) |
| Barrel Length | 16" |
| Barrel Material | 4150 Chrome-Moly-Vanadium |
| Barrel Twist | 1-7" |
| Barrel Finish | Black QPQ |
| Receiver Material | 7075 T6 Forged Aluminum |
| Receiver Finish | Mil 8625 Type 3 Class 2 Hardcoat Anodize |
| Gas System | Carbine-length with low-profile gas block |
| Handguard Type | Gen 2 Enhanced M-LOK monolithic rail |
| Handguard OAL Options | 9" or 15" |
| Handguard Inner Diameter | 1.78" |
| Top Rail | Full-length Picatinny |
| Muzzle Device | A2-style flash suppressor |
| Pivot/Takedown Pins | .250" diameter |
| Included Components | Assembled upper receiver, barrel, handguard, gas block, ejection port cover, forward assist, flash suppressor |
| Not Included | Bolt carrier group, charging handle |
The M4E1 comes fully assembled except for the bolt carrier group and charging handle. You'll need to source those separately—they're the two components most builders replace anyway, so having a choice is a feature. Once you drop in a BCG and charging handle, it'll be ready to mate with a lower receiver.
Yes. The barrel is chambered for 5.56 NATO and will reliably cycle both 5.56 NATO and .223 Remington ammunition.
The handguard has a 1.78" inner diameter that accommodates most muzzle devices and standard 1.5" suppressors. Verify the specific suppressor's dimensions if you're running something unusual, but standard suppressors will fit without issue.
The M4E1 comes with either a 9" or 15" M-LOK handguard. Shorter handguards suit shorter overall length builds or closer-quarters use, while longer handguards give you more rail space for accessories and a more traditional carbine profile. Both are monolithic and provide the same quality rail system—it's up to your intended use and preference.
