M4E1 5.56 Assembled Upper Rcvr Threaded W/Ar15 Semi-Cut Blk

The Aero Precision M4E1 5.56 assembled upper receiver with threaded barrel nut opening gives you a modernized AR15 platform built from 7075-T6 aluminum forgings. This is a complete, ready-to-use upper receiver—port door and forward assist are pre-installed—designed to drop into any mil-spec AR15 lower receiver and accept standard AR15 barrel nuts. The M4E1's angular machined profile delivers that premium billet look without the billet price tag, making it a smart choice for builders who want clean aesthetics and proven performance on a realistic budget.

The threaded design accepts any mil-spec AR15 barrel nut, giving you flexibility in your build. Machined from military-spec 7075-T6 aluminum and precision-finished to work reliably with all standard AR15 parts, the M4E1 upper is as functional as it is distinctive. The enhanced forging profile and refined picatinny rail blend seamlessly with Aero Precision's Enhanced and ATLAS series handguards, so you can build a cohesive receiver set that looks and feels unified. M4 feedramps are built into the receiver, and the .250 takedown pin holes ensure compatibility with any mil-spec lower you pair it with.

Whether you're building a 5.56 rifle for hunting, sport shooting, or home defense, the M4E1 upper receiver gives you a solid foundation. The threaded forward assist roll pin is included, and the port door comes pre-installed, so there's nothing left to source before assembly. This is a no-compromise choice for shooters who refuse to compromise on build quality or value.

Key Features

• Forged 7075-T6 aluminum construction with angular machined profile
• Threaded barrel nut opening for standard AR15 compatibility
• Port door and forward assist pre-installed
• M4 feedramps integrated into receiver
• .250 takedown pin holes (mil-spec)
• Enhanced picatinny profile compatible with Aero Precision handguards
• Threaded forward assist roll pin included

Specifications

Frequently Asked Questions

Is the M4E1 upper receiver compatible with my mil-spec AR15 lower?

Yes. The M4E1 upper receiver is precision machined to work with all mil-spec AR15 lower receivers and parts. The .250 takedown pin holes conform to mil-spec standards, ensuring a proper fit and function.

What barrel nut does this threaded upper receiver use?

The M4E1 upper receiver features a threaded barrel nut opening that accepts standard AR15 barrel nuts. This gives you flexibility in barrel selection and compatibility with widely available components.

What comes pre-installed on this upper receiver?

The port door, forward assist, and threaded forward assist roll pin are all pre-installed. You receive a complete, ready-to-assemble upper receiver—no additional parts are needed before mating it to your lower and installing a barrel.

What handguards work with the M4E1 upper receiver?

The M4E1's enhanced picatinny profile is designed to blend seamlessly with Aero Precision's Enhanced and ATLAS series handguards. It is also compatible with other mil-spec AR15 handguards that accept standard picatinny rails.