Aero Precision 5.56 NATO M4E1 ATLAS S-ONE Completed Upper

Aero Precision 5.56 NATO M4E1 ATLAS S-ONE Completed Upper

$449.99$489.99 $449.99$489.99



Aero Precision 5.56 NATO M4E1 ATLAS S-ONE Completed Upper

Barrel lengths available in 10.5″ or 16″

Aero Precision 5.56 NATO M4E1 ATLAS S-ONE Completed Upper is the most efficient way to assemble your own custom firearm; fully assembled and warrantied by Aero Precision.  The S-ONE handguards are designed with size and weight in mind, providing the perfect addition to your lightweight build. Aero Precision’s proprietary ATLAS attachment system is a durable and dependable mounting platform, maintaining a slim profile while still providing the strength and stability customers have grown to love from Aero Precision handguards.

*NFA Rules apply for the 10.5″ barreled model.
**The muzzle devices are NOT pinned nor welded to the barrel.
***Does not include Bolt Carrier Group or Charging Handle.

M4E1 Threaded Upper Receiver Features:

  • New enhanced forging that gives the upper receiver a “billet look”
  • M4 Feedramps
  • .250 takedown pin holes
  • Laser engraved T-marks
  • Includes port door and forward assist installed

ATLAS R-ONE Handguard Features:

  • Front and rear picatinny rail
  • Eliminated center of top rail for weight reduction
  • Indexing grooves in 12:00 position for positive grip control
  • Quick disconnect sling socket at the 3, 6 and 9 o’clock positions
  • Compatible with low profile gas blocks
  • 1.3” Inside diameter
  • 1.5” Outside diameter

5.56 Mid-Length Barrel Features:

  • 5.56 NATO 10.5″ Carbine or 16″ Mid-length, 1/7 twist, 4150 CrMoV, QPQ, gas port drilled
  • .750 gas block journal
  • Mid-length gas system, .0785 gas port
  • M4 Feed Ramp Extension
  • HP and MPI tested
  • Standard A2 flash hider


Also available in other configurations

….with ATLAS R-ONE Handguards

….with Enhanced Handguards


  • M4E1 Threaded Assembled Upper Receiver
  • ATLAS S-ONE Handguard
  • 10.5″ or 16″ 5.56 CMV Barrel
  • Low Profile Gas Block and Gas Tube
Product Information

Manufacturer:  Aero Precision
Assembled: Yes
Finish: Anodize
Color: Black
Caliber: 5.56 NATO
Platform: AR15
Complete Upper Series: ATLAS
Handguard OD:  1.5″
Handguard ID: 1.3″
Handguard Type: M-LOK
Gas Block Diameter: .750
Muzzle Device: A2 Flash Hider
Muzzle Threads: 1/2×28 TPI
Barrel Length: 10.5″ | 16″
Barrel Finish: QPQ Melonite
MSRP: Varied by model

Arm or Ally is a stocking dealer for all Faxon Firearms, Ballistic Advantage, Rosco Manufacturing, Aero Precision, Toolcraft, Elftmann Tactical, HIPERFIRE and more. See our growing inventory of AR Parts and Reloading Components.

Additional information

Barrel Length

10.5", 16"


Aero Precision

Gas System

Carbine, Mid-Length

Gas Block Diameter


Muzzle Thread

1/2 x 28


5.56 NATO

You may use the 10.5″ Completed Upper with a lower receiver that is a Registered SBR, Machine Gun, or Pistol. Possession of this barrel along with a Non-NFA lower receiver is Prohibited, except when installed on a Pistol configuration firearm.

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