M4E1 350 Legend Assembled Upper M4 20'' Carbine Threaded Fde

The Aero Precision M4E1 350 Legend assembled upper receiver gives you a complete, ready-to-build upper assembly in FDE—one of the smartest moves for a 350 Legend AR build. This 20-inch carbine upper comes with the port door and forward assist already installed, so you're not hunting down small parts before you can start assembling. Pair it with a bolt carrier group and charging handle of your choice, and you've got a solid foundation for a short-range hunting rifle, truck gun, or suppressed subsonic platform that's become genuinely useful for hunters in states with straight-wall cartridge seasons.

What sets the M4E1 apart is the refined upper forging design. Aero engineered this to deliver a "billet look"—sharp, refined lines that suggest precision machining—while maintaining the strength and reliability of a properly forged receiver. The new Picatinny profile on the flat-top integrates seamlessly with Aero's Enhanced Series handguards, so your rail sits perfect and flush. Standard M4 feedramps, .250 takedown pin holes, and laser-engraved T-marks round out the details. Threading on the muzzle gives you the option to run a muzzle brake, flash hider, or suppressor right out of the box.

350 Legend is gaining traction as a hunting cartridge where it's legal, and a dedicated upper receiver makes sense if you're running multiple uppers on one lower receiver. The FDE finish is durable and pairs well with modern handguards and tactical furniture. Whether you're building a dedicated 350 Legend rig or adding another upper to your collection, the M4E1 delivers Aero's quality without the complications.

Key Features

• Enhanced forging with billet-like appearance and precision detailing
• Compatible Picatinny profile works seamlessly with Aero Enhanced Series handguards
• Port door and forward assist pre-installed
• M4 feedramps for reliable feeding
• Threaded muzzle for muzzle devices and suppressors
• Laser-engraved T-marks for sight alignment
• .250 takedown pin holes for standard AR lower receivers
• FDE (Flat Dark Earth) finish

Specifications

Frequently Asked Questions

What do I need to complete this upper receiver into a working rifle?

This is an assembled upper receiver; you'll need to add a bolt carrier group and charging handle to make it functional. You'll also need an AR-15 lower receiver (or AR-10, depending on your platform compatibility) to complete the rifle.

Is this upper compatible with standard AR-15 lower receivers?

Yes. The M4E1 uses .250 takedown pin holes, which are standard for AR-15 and most AR-platform lower receivers. It will work with any compatible lower.

Can I attach a suppressor or muzzle brake to this upper?

Yes. The muzzle is threaded, so you can attach a suppressor, muzzle brake, flash hider, or other threaded muzzle device of your choice.

What handguards work with the M4E1 Picatinny profile?

The Picatinny profile is designed to integrate seamlessly with Aero Precision's Enhanced Series handguards. It will also accept standard Picatinny-mounted AR handguards and rails.