Aero Precision 5.56 NATO M4E1 ATLAS R-ONE Complete Upper

Aero Precision 5.56 NATO M4E1 ATLAS R-ONE Complete Upper


Fully Assembled and Warrantied by Aero Precision


Aero Precision 5.56 NATO M4E1 ATLAS R-ONE Complete Upper

Available in 10.5″ Carbine or 16″ Mid-Length

Aero Precision 5.56 NATO M4E1 ATLAS R-ONE Complete Upper is the most efficient way to assemble your own custom firearm; fully assembled and warrantied by Aero Precision. The R-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:

  • Full top picatinny rail for optional attachments
  • 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
  • Compatible with mil-spec AR15 upper receivers and barrels

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:

APAR700702M2 – 10.5″ Carbine w/ 9″ ATLAS R-ONE MLOK
APAR700705M7 – 16″ Mid w/ 15″ ATLAS R-ONE MLOK

Also available with the ATLAS S-ONE Handguards


  • M4E1 Threaded Assembled Upper Receiver
  • M-LOK ATLAS R-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: APAR700702M2 | APAR700705M7
Assembled: Yes
Finish: Anodize
Color: Black
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 $484.99

Arm or Ally is a stocking dealer for  Aero Precision, Faxon, Polymer80, Ballistic AdvantageToolcraft, SB Tactical, Holosun and more. See our growing inventory of AR Parts, Firearms and Reloading Components.

Additional information

Weight N/A
Dimensions N/A
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.