M4E1 Threaded 20" 5.56 Complete Upper Receiver w/ ATLAS S-ONE Handguard

Aero Precision AR15 Gen 2 Complete Upper, 20" 5.56 Rifle Length Barrel, ATLAS S-ONE Handguard

M4E1 Threaded 20" 5.56 Complete Upper Receiver w/ ATLAS S-ONE Handguard Product Sku: APPG700210

This complete upper includes our new ATLAS S-ONE Handguard! The S-ONE line of handguards are designed with size and weight in mind, providing the perfect addition to your lightweight build. Our 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.


  • M4E1 Threaded Assembled Upper Receiver
  • ATLAS S-ONE Handguard of choice
  • 20" 5.56 Rifle Length CMV Barrel
  • Low Profile Gas Block and Rifle Length Gas Tube
  • Product comes assembled
  • This complete upper does not include BCG or Charging Handle. These products may be selected as add-ons under the FINISH YOUR BUILD tab

M4E1 Threaded Upper Receiver Features:

  • New enhanced forging that gives the upper receiver a "billet look"
  • New picatinny profile that blends seamlessly with our Enhanced Series Handguards
  • 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
  • Compatible with mil-spec AR15 upper receivers and barrels
  • Learn More about our NEW ATLAS S-ONE Hanguards

20" 5.56 Rifle Length CMV Barrel Features:

  • 5.56 NATO 20" Rifle Length, 1/7 twist, 4150 CrMoV, QPQ, gas port drilled
  • .750 gas block journal
  • Government Profile
  • Rifle length gas system, .0785 gas port
  • M4 Feed Ramp Extension
  • HP and MPI tested
  • Standard A2 flash hider
Made In America? Yes
Platform AR15
Series ATLAS
Caliber 5.56 NATO
Barrel Length 20"
Weight(s) 61 oz
Other NOTE: Weights above include Gen 2 Upper, Handguard, Barrel, Muzzle Brake and Mounting Hardware.

Customer Reviews

2 Item(s)

Shipped fast shoots great with 62 grain Review by Rusty
This upper looks amazing everyone dotes on how good it looks I love the slim profile of the hand guard switched to this upper from a 16 inch barrel and they weigh the same. Shoots nice and smooth. This upper did not shoot good with 55 grain 556 or 223. Went to 62 grain and it shoots fine. (Posted on 2/3/2018)
Did not meet expectations Review by Kenneth
I wanted to return this entire upper based on the performance of the barrel. The sad part was that I had my expectations high for this 20 inch complete upper because of the outstanding accuracy of another 16 inch Aero Precision complete upper that I shot prior. The best I could achieve with this upper was one and one half MOA at 100 yards with 77 grain ammunition. The groups for 4 other brands of 55 grain ammunition were all over 4 inches at 100 yards. I felt like I was shooting a shotgun. I was very disappointed with the barrel for this complete upper. Besides the aesthetics to this complete upper. I am having buyers remorse. I am planning to replace the barrel as soon as I can afford it. I can only give it 2 stars on value and quality because it will cost me just the same as if I had purchased an upper with a guarantee 1 MOA barrel. (Posted on 12/10/2017)

2 Item(s)

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