Aero Precision M4E1T Complete - Upper 10" Barrel 300Blk

The Aero Precision M4E1T Complete Upper with 10" barrel in .300 Blackout is a ready-to-run upper receiver assembly built for shooters who want a compact, versatile platform without the assembly hassle. This is a genuine Aero Precision complete upper—it ships assembled and ready to marry to your lower receiver (you'll supply your own bolt carrier group and charging handle). The 10" barrel strikes a practical balance for .300 Blackout, whether you're running a short-stroke rifle, a pistol-caliber trainer, or a dedicated subsonic hunting build.

At the heart of this upper is Aero's M4E1T threaded upper receiver, featuring their enhanced forging that delivers a billet-like appearance without the weight penalty of actual billet. The receiver includes M4 feed ramps, a full-diameter take-down pin boss (.250" holes), laser-engraved T-marks, port door, and forward assist already installed. The barrel itself is genuine 4150 Chrome Moly Vanadium with QPQ corrosion-resistant finish inside and out, chambered in .300 Blackout with a 1-in-7 twist rate. It comes with a low-profile gas block and pistol-length gas system, plus a standard A2 flash hider (not pinned or welded, so it's user-removable for suppressors or other muzzle devices). The barrel is HP and MPI tested for reliability.

The ATLAS R-ONE handguard is Aero's slim, lightweight mounting solution. It features a full-length top picatinny rail for optics or accessories, quick-disconnect sling sockets at 3, 6, and 9 o'clock positions, and is machined to clear low-profile gas blocks. The handguard's proprietary ATLAS attachment system keeps the profile trim while maintaining the rigidity Aero Precision users expect. With 1.3" inner diameter and 1.5" outer diameter, it fits standard mil-spec AR15 upper receivers and barrels.

This is a straightforward, no-nonsense complete upper from a builder you can trust. Bolt carrier group and charging handle are not included—everything else you see is there.

Key Features

• M4E1T threaded upper receiver with enhanced forging and billet-like finish
• Full top picatinny rail for mounting optics and accessories
• ATLAS R-ONE handguard with QD sling mounts at 3, 6, and 9 o'clock
• 10" .300 Blackout 4150 CMV barrel with QPQ finish
• 1-in-7 twist rate optimized for .300 Blackout
• Low-profile gas block and pistol-length gas system
• M4 feed ramps and laser-engraved T-marks
• HP and MPI tested barrel for reliability
• Assembled and ready to install on a compatible lower receiver

Specifications

Frequently Asked Questions

What do I need to complete this upper receiver?

This is a complete upper assembly, so you'll need a lower receiver to pair it with. You'll also need to source a bolt carrier group (BCG) and charging handle, which are not included. Once you have those three components, you have a functioning rifle.

Is this .300 Blackout upper compatible with a standard AR-15 lower?

Yes. This upper is built on the M4E1T platform and is compatible with mil-spec AR15 upper receivers and barrels. It will work with any mil-spec AR-15 lower receiver.

Can I use a suppressor with this barrel?

The included A2 flash hider is not pinned or welded, so you can remove it and install a suppressor threaded to 5/8x24. The barrel itself is .300 Blackout, which is commonly used with suppressors for subsonic applications.

Will this fit in an AR pistol or short-stroke rifle build?

Yes. The 10" barrel with pistol-length gas system is suitable for both AR pistols and short-stroke rifle configurations when paired with the appropriate lower receiver and buffer system.

What's included in the box?

The complete upper includes the M4E1T threaded upper receiver, ATLAS R-ONE handguard, .300 Blackout CMV barrel, low-profile gas block, and A2 flash hider. Bolt carrier group and charging handle are sold separately.