5.56 CMR Rail (9.5in - 14in)

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Our patented CMR rail system is a lightweight, rugged, one piece, free float hand guard that, when installed, gives the upper a continuous 12 o'clock rail.

The CMR system clamps to a proprietary barrel nut that can be installed on 5.56/.223 based AR platform systems. It was designed with the top 1913 rail for mounting the most common accessories, yet does away with the need for 1913 rail at the 3, 6, and 9 o'clock positions.

Here, other accessories can be directly mounted to it with a dedicated, simple, light-weight, mount. However, it does allow for 1913 rail to be added, if needed, for some less common accessories. Additionally, we built in anti-rotation QD sling swivels in 4 positions.

The main objective was to have a smaller, lighter weight, more ergonomic, hand guard that maintains or enhances functionality for the end user. As professional end users ourselves, we know the importance of keeping things simple and that was our design intent here... a K.I.S.S. (keep it simple, stupid) system.


Material: 6061 T6

Finish: Type III hard coat anodized

Integrated QD Attachment sockets - Limited Movement


9.5in-9.4oz with barrel nut | 7.3oz without barrel nut

11in-10.4oz with barrel nut | 8.3oz without barrel nut

12in-10.7oz with barrel nut | 8.6oz without barrel nut

13in-11oz with barrel nut | 9oz without barrel nut

14in-11.8oz with barrel nut | 9.6oz without barrel nut


9.5in (9.418")

11in (10.994")

12in (12.56")

13in (13.688")

14in (14.25")


1.56 (body of tube) 1.75 (at QD sling swivels)



Inside diameter:


Rails: 1913 spec rail on top

Made in USA


- Currently our gas block is the only one that Centurion Arms can guarantee to fit under the CMR. This is due to the CMR's extreme low profile.

- Screws, proprietary barrel nuts, and wrench are included with the purchase of all rail systems. Replacement screws, barrel nuts, and wrenches are available to purchase if necessary.


  • 5
    CMR 12.5

    Posted by Kolton on Jan 30th 2021

    Love this rail!!! I chose the gen1 cause i think it looks better and its already super light. Im using it with a 12.5 centurion barrel. The inside diameter was tight mainly due to the front QD’s. Love the look and fit. Always happy with the products and the service.

  • 5
    CMR Rail

    Posted by Todd on Jan 26th 2021

    Centurion continues to deliver top notch quality on all their products. The fitment of the rail is perfect, the thought put into the design shows, and there is nothing bad that can be said.

  • 5
    New favorite rail

    Posted by Braxton on Aug 12th 2020

    I have a 11in cmr on a 12.5 centurion arms carbine barrel . It had very tight fit up and extremely nice finish. Its very ergonomic not so thin it feels weak and not so thick its hard to hold. Havent noticed any problem with heat . I have bought again and referred others to check them out. On a company level i have never dealt with more professional, curtious and knowledgeable staff.

  • 5
    cmr rail 13"

    Posted by Brody on Oct 23rd 2019

    A great system that fit perfect with my 14.5-inch barrel pinned and welded. The attachment system is great and the gen2 is even lighter!

  • 5
    5.56 CMR 9.5in.

    Posted by Danny Clark on Aug 10th 2019

    I have one of these on my pistol build with a 10.5" barrel and the end result was great. With a suppressor mounted it's hard to tell where the rail ends and the suppressor begins. This rail is lightweight and slim, My MK18 is a tank compared to this upper. The tangs allow the rail to lock up solid to the upper receiver allowing for perfect alignment. Multiple QD connections are and added plus saving me the expense of add-on QD attachments for a sling. And lastly as I've said in my other reviews for Centurion Arms product the barrel nut design is simple and easy to work with.... no timing to worry about, it just flat out works.

  • 5
    Best rail system ever

    Posted by Darrin Raymond on Aug 10th 2019

    Love the original CMR. Have had it for a little while and it’s perfect for my colt commando. Thank you Centurion!

  • 4
    Fantastic Rail

    Posted by Terry Usher on Aug 10th 2019

    I have one of these rails set up on a 16” build I made about 4 months ago. I love this rail. It’s incredibly solid and extremely slim. Makes for a great lightweight build without sacrificing durability.

  • 5
    Light and reliable.

    Posted by Rick on Aug 10th 2019

    Centurion Arms is a fantastic company! I bought a 13in. CMR for my AR assembly, (my wife's, she wanted light...) the Magnesium lower started off the project. I contacted Centurion Arms, the CMR 13 inch looked like a great fit! The CMR arrived with in the week! I forgot to order the rail covers. I jumped back on the web site ordered
    The FDE, .(manadatory for Arizona shooting!) Two days later they arrived at the door, and were on her carbine. She loves it! The slim grip, the texture on the slim line panels, it fits her perfectly! The folks at Centurion Arms are great people, they put out a quality product, stand behind what they make, and do all they can to help you succeed! I really appreciated the personal note of thanks on the receipt. My next assembly will definitely have a Centurion Arms rail, that's for sure