Centurion Arms Rail


Centurion Arms C4 Rail

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I recently found myself in the market for a carbine length free float rail for an AR build. After reviewing the multitude of rails on the market I opted to go with the Centurion Arms C4 front sight cut out rail.

I decided on this rail for a variety of reasons. They were:

1. It free floats the barrel. Admittedly, for anything other than a precision rifle, free floating the barrel is of minor benefit, however if given the option I feel like you might as well free float.

2. The rail maintains and extends around the Front Sight Base. I am a fan of the standard AR fixed and pinned front sight base as it is bombproof and basically malfunction free. With that in mind I was not interested in any rails that would require the installation of a low profile gas block. The disadvantage to this is carbine length rails are pretty short and run out of space quickly when vertical fore grips, lights, sling mounts, etc. are installed. This is one of the areas in which the carbine cut out C4 rail shines as it retains the pinned front sight base but has rails that extend past the FSB on the sides and bottom, giving more room to add and position accessories.

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3. Easy install that does not require removal of the FSB. As much as I like the pinned front sight base, I hate having to remove them. The Centurion Arms rail’s two piece design makes this a non issue as the FSB does not have to come off for the rail to be installed. It merely clamps around the factory barrel nut, and is an easy do it yourself install. This is also a benefit to those with some type of pinned muzzle device as it will not have to to be removed to install the rail. The handguard cap and delta ring assembly do need to be removed however.

4. Lightweight for its size. The sight cut out rail I purchased weighed in at 10.6 oz.

5. Built in quick detach sling mounts. The rail has built in mounting points for quick detach sling swivels at the front and rear of both sides of the rail. I am a fan of making things as efficient as possible with the fewest parts, and the built in mounting points allow the sling to attach directly to the rail, eliminating the need for a separate bolt on mounting point. The multiple mounting points on each side also allow the user to adjust the sling to their preference.

I purchased my Centurion Arms rail from Rainier Arms and highly recommend them for any of your AR parts needs. I have always had excellent dealings with them. The rail came packaged in a form fitting tube and inside I found the upper and lower pieces of the rail along with the six screws with which to assemble it. No instructions were included however it is fairly simple, straightforward, and self explanatory. If you just have to have them, instructions are available at Centurion Arms website.

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I started by removing the factory handguard cap and delta ring assembly. If you want to retain these pieces for re use later you will need to remove the FSB to uninstall them. I did not, nor did I want to remove the FSB, so I used my handy dremel tool to cut them off. The factory under barrel sling swivel also has to come off but a hammer and punch made short work of the pin that holds it in place.

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With everything removed the upper and lower sections of the rail clamp around the factory barrel nut. Install four screws at the barrel nut portion of the rail and other two screws on the sides near the FSB end and you’re done. Mount the accessories of your choice in the locations of your choice.

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I also have an upper with a Daniel Defense M4 9.5 FSP rail installed and took a few quick comparison photos of the two next to each other. As you can see the DD rail extends slightly further than the Centurion Arms rail however the Centurion Arms rail has continuous top rail while the DD has a gap for the proprietary barrel nut. The DD rail also lacks the built in sling mounts.

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After several months of use I have no complaints and have found the rail does what it’s supposed to do with no fuss or drama.  It locks solidly to the upper and has no noticeable flex.  Subjectively it feels slimmer in the hand than other full railed handguards I’ve handled.  I would recommend Centurion Arms rails to anyone looking for a railed handguard.

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  1. I’m having such a hard time choosing between. A Daniel Defense Omega X 12.0 FSB and the Centurion 12.0 FSB. I like the feel of the Omega’s as they are thin, But I have not had my hands on the Centurion’s yet. Not that it matters, but the Centurion looks cool. I like that you can see the gas tube the entire length of the rail.

  2. Out of curiosity, how long is the barrel on this? Looks like 12.5, but I might be wrong. I’ve been itching to do something almost identical once I get back to a “free” state. Monty, the founder of Centurion, once expressed the superiority of 12.5″ barrels for SBR applications over the shorter versions.

  3. Adam,

    Appreciate this review, although a lot of days and nights have past, but this review, especially the photo comparisons, helped me out.

    The Daniel Defense was on my short list with this Centurion, but the Centurion won out because the design engineer at DD was fast asleep.
    DD decided that they would forgo the quick release sling points and instead, retain the annoying swivel stud and sling mount.

    DD made my decision to buy a Centurion for me. Ordered one yesterday. When one spends $250+ on a free float rail, I shouldn’t have to buy a quick release sling adapter post sale. That’s another $30

    Don’t need the DD sling and swivel stud, my atlas will happily clamp to the Centurion rail 🙂

    Thanks again for writing this review, it really was appreciated

    Sam G
    retired vet


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