Aero Precision M4E1-T Complete Upper, 14.5" 5.56 Mid Barrel w/Pinned Epsilon SL, 12.7" ATLAS R-ONE MLOK HG - Anodized Black

Fully Assembled and Warrantied by Aero Precision
SKU: APAR700704M68

Original price was: $725.00.Current price is: $516.88.

In Stock

Only 1 left in stock

Aero Precision M4E1-T Complete Upper, 14.5″ 5.56 Mid Barrel w/Pinned Epsilon SL, 12.7″ ATLAS R-ONE MLOK HG – Anodized Black

The Aero Precision Complete Upper Receiver epitomizes speed, efficiency, and dependability for fashioning a semi-custom AR15 rifle. Crafted with meticulous precision, this 5.56 NATO M4E1 Threaded Complete Upper boasts a 14.5″ Mid-Length barrel and a 12.7″ ATLAS R-ONE handguard. Meticulously machined, comprehensively assembled, and subject to rigorous test-firing by skilled Aero Precision armorers, it guarantees unparalleled performance.

We’ve taken the pain out of building a legal 14.5″ rifle build. These pinned and welded 14.5″ complete uppers feature an Epsilon 556SL that is permanently affixed to the muzzle providing an overall legal length of 16″. Worried you might want to change your gas block? No worries! The outer diameter of the Epsilon 556SL allows you to easily slide your gas block over the muzzle device making it easy to change or service your gas system.

If you’ve had a 14.5″ build planned, but didn’t want to deal with the hassle of getting it pinned and welded or being stuck with a specific configuration, then our 14.5 pinned and welded barrels/uppers are for you!

* Does not include Bolt Carrier Group or Charging Handle.

* The included muzzle brake is pinned to this barrel. Per the National Firearms Act, the muzzle brake MUST be pinned and welded to achieve the necessary 16″ as defined by the ATF for a rifle build.


  • M4E1 Threaded Assembled Upper Receiver – Anodized Black
  • 12.7″ M-LOK ATLAS R-ONE Handguard – Anodized Black
  • 14.5″ 5.56 NATO Mid-Length Barrel
  • Low-profile Gas Block and Gas Tube
  • VG6 Epsilon SL – Pinned to Barrel

M4E1 Threaded Upper Receiver Features:

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

ATLAS R-ONE Handguard Features:

Aero Precision’s ATLAS attachment system is a secure and dependable mounting platform, maintaining a slim profile while still providing the strength and stability customers have grown to love from Aero Precision handguards.

  • Continuous top Picatinny rail
  • 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 NATO Barrel Features:

  • 5.56 NATO 1/7 twist, 4150 CrMoV, QPQ finish
  • .750 gas block journal
  • Mid-Length gas system
  • M4 Feed Ramp Extension
  • HP and MPI tested

Product Information


Aero Precision








12.7" M-LOK


5.56 NATO



Gas System


Twist Rate


Barrel Finish

QPQ Nitride

Muzzle Thread





4150 Chrome Moly Vanadium, 6061-T6 Aluminum


Standard AR15 components

Made in USA


Arm or Ally

Arm or Ally is a stocking dealer for all Aero Precision, Faxon Firearms, Ballistic Advantage, HOLOSUN, Toolcraft, Elftmann Tactical, Timney, TriggerTech, HIPERFIRE and was named the #1 Overall E-Commerce Dealer for Aero Precision Products in 2020!

See our growing inventory of AR Parts, Parts for Glock and Reloading Components.