CM4 5.56 Forged Upper Receiver

Usually Ships in 1-3 Business Days - Custom Cerakote Lead Times Vary (See Disclaimer Below)
(4 reviews) Write a Review

Our forged upper receivers are a great compliment to our forged lower receivers and are batched either with a MIL-Spec or Thermal Fit bore. 

MIL-Spec inner dimension measures at 1.000 -0.0/+0.002"

Thermal Fit inner dimension measures at .997 -0.0/+0.001" and requires the application of heat in order to provide a solid mate to the recommended barrel extension.  By heat we mean more than granny's hair dryer.


-For Use with M4 Barrel extensions

-Assembled Upper Receivers come with ejection port cover and forward assist installed
-Made in America on American-made machines

*** We recommend gunsmith installation for all of our parts.  We cannot warranty items damaged by improper installation.

Custom Cerakote™ Disclaimer:


Custom Cerakote is completed per order.  Our Cerakote room runs one color at a time so your ship date will be subject to the color rotaion at the time the order is placed.  You will receive an email confirmation once the item has actually been packaged to ship.

Cerakote™ items are not guaranteed to match separate batches or Cerakote completed by outside parties.  While we strive to keep our mix uniformed for our own products, we can't say for certain what Walter and Jesse cooked up in their lab out in Albuquerque.

7075 T6 Forgings
MIL-Std 1913 Rail
Hardcoat Anodized per MIL-A-8625F, Type III, Class 2


  • 5

    It's made by Centurion so that should explain all . If you are reading this you have already crawled out of the primordial ooze and have taken steps towards investing in quality so just hit that Add To Cart button & treat yourself because you deserve it & don't want to let down your family & peers .

  • 5
    One of the best upper receivers I have used

    I have had the experience to try a number of different branded upper receivers and the Centurion CM4 is right up there with the best, if not the best, that I have tried. There was very little slop with the lowers I tried these receivers on. The inside diameter for the barrel extension was slightly undersized, which allowed for an extremely tight fitting barrel. On top of all this, the T-markings and logo are subdued, not annoyingly white! Keep up the great work Centurion!

  • 5
    Upper Receiver Excellence

    Flawless machining, consistent finish, and precise fit. You always hear people talking about Centurion Arms with high regard, and this upper receiver just reaffirms the general consensus. Outstanding product and customer service. Will definitely choose Centurion Arms for future builds.

  • 5
    Zero slop

    Fits my KAC and BCM lowers with ZERO slop, yet the takedown and pivot pins still move freely.

    I don’t think I’ll be building with any other uppers going forward.