M4E1 5.56 Assm Uppr Rcvr Gov 10.5'' Bbl Carbine W/7''Hg & Fsb

The Aero Precision M4E1 5.56 assembled upper receiver is a fully-built upper designed for shooters who want to complete their AR-15 build with quality components already installed and tested. This carbine upper comes with a 10.5\" barrel, carbine-length gas system, and a 7" handguard with front sight base—everything except the bolt carrier group and charging handle, which are intentionally left out so you can choose those parts to match your build. Whether you're assembling a compact AR pistol or planning an SBR (with proper NFA registration), the 10.5" barrel length delivers the versatility serious builders expect in a purpose-built upper receiver.

At the core is Aero's forged M4E1 receiver, which pairs the ergonomic, billet-style profile with true mil-spec compatibility for BCGs and charging handles. The 4150 chrome-moly-vanadium barrel is chambered in 5.56 NATO and safely handles .223 Remington as well, with 1-7\" rifling for reliable bullet stabilization across both cartridges. The A2 flash suppressor comes installed (unfastened, not pinned) and the handguard's 1.78" bore clears most muzzle devices and suppressors you'll want to run. Black QPQ finish on the barrel and Parkerized steel parts resist corrosion in the field, while the 7075 T6 forged aluminum receiver delivers durability without the weight.

The included Gen 2 Enhanced M-LOK handguard creates a monolithic mounting platform with full-length top Picatinny rail and M-LOK slots at multiple positions for accessory mounting. Textured grip flats on the receiver add purchase and visual character. QD sling attachment points at 3, 6, and 9 o'clock give you flexible carry and deployment options. This is a straightforward, no-compromise upper receiver built for hunters, precision shooters, and AR builders who refuse to compromise on fit, finish, or function.

Key Features

• Fully assembled upper receiver—install your choice of bolt carrier group and charging handle
• 10.5\" 4150 chrome-moly-vanadium barrel, 1-7\" twist, 5.56 NATO/.223 Remington
• Forged M4E1 receiver with mil-spec compatibility and monolithic mounting platform
• Carbine-length gas system for reliable cycling in short-barreled builds
• 7\" M-LOK handguard with integrated front sight base gas block
• Full-length Picatinny top rail with multiple M-LOK attachment points
• QD sling swivel sockets at 3, 6, and 9 o'clock positions
• A2 flash suppressor installed (not pinned or welded)
• 1.78\" handguard bore diameter clears most suppressors and muzzle devices
• Black QPQ barrel finish and Parkerized steel parts for corrosion resistance
• Textured receiver flats for improved grip and appearance

Specifications

Frequently Asked Questions

What do I need to complete this upper receiver?

You'll need a bolt carrier group and charging handle to finish the build. Both are intentionally left off so you can choose components that match your preferences and budget. Everything else—barrel, gas system, handguard, and rail system—comes installed and ready to go.

Can I use this upper for an AR-15 pistol or SBR build?

Yes. The 10.5" barrel length and carbine-length gas system work for both configurations. If you're building an SBR, you'll need to follow all applicable NFA regulations and obtain the proper federal tax stamp and registration before assembly.

Will suppressors fit on this upper?

The handguard's 1.78\" inside diameter clears most suppressors up to 1.5" in diameter, so you have good options. Always verify your specific suppressor's dimensions before installation.

What ammunition can I shoot?

The barrel is chambered in 5.56 NATO and safely handles both 5.56 NATO and .223 Remington ammunition. The 1-7\" rifling stabilizes a wide range of bullet weights in both cartridges.

Is the flash suppressor pinned or welded?

No. The A2 flash suppressor comes installed but not pinned or welded, so you can remove or replace it if you prefer a different muzzle device.