MPN: APAR700305M48 / APAR700705M48


  • Caliber: 5.56 NATO
  • Finish: Type III Class 2 Hardcoat Anodized Finish
  • Upper Receiver: Aero Precision M4E1 Threaded Upper - 7075-T6 Aluminum
  • Handguard: 15-Inch ATLAS S-ONE or R-ONE M-LOK Handguard
  • M4 Feed Ramps: Yes
  • Muzzle Device: A2 Flash Hider
  • Barrel: 20" 1:7 QPQ Coated 4150 Chrome Moly Vanadium Barrel
  • Muzzle Thread Pattern: 1/2"-28 TPI
  • Gas Block: Aero .750" Low-Profile Gas Block
  • Gas Tube: Rifle Length Gas Tube
  • Bolt Carrier Group: Not Included
  • Charging Handle: Not Included
  • HP and MPI Tested
  • Government Profile

*This upper assembly does not come with Bolt Carrier Group and Charging Handle

*ATLAS S-ONE Handguard: Front and rear picatinny rail section. Eliminated center of top rail for weight reduction.

*ATLAS R-ONE Handguard: Full top picatinny rail


  • Weight: ~3.65 lbs.
  • Length: ~28.4"


  • AR-15 lower receiver


  • 1x Aero Precision 10.5" M4E1 5.56 Complete Upper Assembly


Even the humble 5.56 can be a very capable round at long ranges with a longer barrel. It is accurate and straight-shooting, and with a long-barreled AR can be used for shooting targets at a fairly long distance.

If you are looking to build a long-range AR-15, chambered in 5.56, Aero Precision has got you covered with their 20" M4E1 5.56 Complete Upper Assembly. This upper assembly comes with a 20-inch long barrel made from 4150 Chrome Moly Vanadium steel. It is super durable and better at heat dissipation as well. The barrel has a 1/2"-28 thread pitch and comes equipped with an A2 style flash hider.

Smooth Shooting

On the barrel, it has a low-profile gas tube and a long rifle-length gas tube to complement the 20-inch barrel. This results in a very smooth recoil impulse. This upper assembly also has a modern slim profile handguard. You can choose either the Aero Precision ATLAS S-One or R-One handguard, both of which are made from T6 aluminum, have M-Lok slots and QD sling slots with scalloped rails. The S-One has a small Picatinny rail section on the top for sights, whereas the R-One has a full-length Pic Rail.

The receiver itself is made from Aircraft grade aluminum and features a forward assist and port door. Along with the barrel, the upper receiver is also High Pressure Tested and Magnetic Particle Inspected to get rid of any minor imperfections and cracks in the metal.

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  • This Item: Aero Precision 20" M4E1 5.56 Complete Upper Assembly
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    MSRP: $675.00
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