Aero Precision 5.56 NATO M4E1 ATLAS S-ONE Complete Upper

Aero Precision 5.56 NATO M4E1 ATLAS S-ONE Complete Upper


Fully Assembled and Warrantied by Aero Precision


Aero Precision 5.56 NATO M4E1 ATLAS S-ONE Complete Upper

Available in 10.5″ Carbine or 16″ Mid-Length

Aero Precision 5.56 NATO M4E1 ATLAS S-ONE Complete 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 S-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 Barrel Features:

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

Choose between 2 Configurations:

APAR700302M2 / APAR700312M2 – 10.5″ Carbine w/ 9″ ATLAS S-ONE MLOK
APAR700305M7 / APAR700315M7 – 16″ Mid w/ 15″ ATLAS S-ONE MLOK

Also available with the ATLAS R-ONE Handguards


  • M4E1 Threaded Assembled Upper Receiver
  • M-LOK ATLAS S-ONE Handguard
  • 10.5″ or 16″ 5.56 CMV Barrel
  • Low Profile Gas Block and Gas Tube
  • Product comes assembled
  • This complete upper does not include BCG or Charging Handle.
  • The muzzle brake that comes with this complete upper receiver is NOT pinned nor welded to this barrel.


Product Information

Manufacturer:  Aero Precision
Brand: Aero Precision
SKU: APAR700302M2 | APAR700312M2 | APAR700305M7 | APAR700315M7
Assembled: Yes
Finish: Anodize | Cerakote
Color: Black | FDE
Caliber: 5.56 NATO
Platform: AR15
Complete Upper Series: ATLAS
Handguard Dims: OD:  1.5″ | 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: $434.99 to $514.99

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


Black, FDE

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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