Colt AR15A4 20 inch Upper Receiver Assembly

(3 reviews)
Current Stock:

The Colt AR15A4/M16A4 Upper Assembly is used on current issue M16A4 model rifles as well as civilian AR15A4 model rifles. This upper receiver allows for a free-floated barrel and also features a gas-block mounted fixed front sight post with bayonet lug and removable carry handle with integrated A2 rear sight. The barrel is Colt's standard 20" chrome lined M16 barrel with an A2 flash hider up front.

Package Contents

  • Colt AR15A4 Complete Upper Assembly
  • Complete M16/M4 Full Auto Bolt Carrier Assembly
  • Charging Handle
  • Fixed Post Front Sight
  • Removable Carry Handle


  • 20 Inch 1/7 twist Mil-Spec chrome lined MP tested barrel
  • Unique direct gas operating system eliminates the conventional operating rod and results in fewer and lighter components
  • Accommodates the full range of 5.56mm ammunition, including the NATO M855/SS109 and U.S. M193, utilizing a rifling twist of 1 turn in 7"
  • Straight-line construction disperses recoil straight back to the shoulder, increasing handling capabilities, especially during repeated fire
  • Cartridge case deflector allows easy operation in both right and left handed shooting positions for increased tactical applications
  • Muzzle compensator further reduces muzzle climb and helps eliminate flash and dust signatures
  • Ejection port cover protects the chamber from dust and mud
  • Field strips easily without special tools for simple field user maintenance
  • Flat top receiver allows for removable carrying handle and easy mounting of accessories
  • High strength materials for greater comfort and effectiveness
  • Caliber - 5.56mm
  • Gas Direct system, Locking bolt
  • Front Sight - Adjustable front
  • Rear Sight - Target sight adjustable for windage and elevation
  • Flash Hider


  • 5
    Colt AR15A4 20 inch Upper Receiver Assembly

    Posted by Unknown on 10th Oct 2021

    The appearance and finish of the upper receiver is excellent. I am looking forward to getting it to the range and sighting it in. Product delivery time was very quick and I will definitely make additional purchases in the future.

  • 5
    A.U. comes through again, and again, and again...

    Posted by ROGER FELLOWS on 25th Mar 2020

    You'll never be sorry you bought the best (Colt), from the company that can't be beat - ARMS UNLIMITED !!!

  • 5
    Great Deal!

    Posted by Moose on 2nd Jul 2018

    I’ve had mixed results with AU, but this was a home run on the positive! Brand New, Colt Cage Code (instead of the ‘C’ you usually see), M4 Feed Ramps and a Carry Handle. Great deal for the money on a somewhat hard to find upper!