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View Full Version : Centurion Arms C4 Rail System - Mid-Length Cutout Rail Hand Guard



Eric
23 July 2013, 00:40
I was ready to update my 16" BCM mid-length with a rail system and I had a few specific requirements that steered me toward the Centurion C4 Rail System.
- the ability to leave the existing fixed front sight in place
- rail sections that extend around the front sight tower for mounting a white light
- built in QD attachment points for sling mounting

This just about sounded like an advertisement for the Centurion Arms C4 Mid-Lenth Cutout Rail System. (https://www.centurionarms.net/index.php?option=com_virtuemart&page=shop.product_details&flypage=cutout-rails.tpl&product_id=78) I've had the opportunity to check out Centurion products on some other instructor's weapons and have been impressed. They've earned a great reputation in the industry for a reason.

Instead of doing a detailed rehash of installation on the C4 rail, read up on it on Centurion Arms web site (great photos and directions!).

Specs from the manufacturer:
Material: 6061 T6
Finish: type 3 hard coat anodized
Weight: 12.4 oz with screws; 1.1oz with standard barrel nut
Length: Top 9 1/4in Sides 11 1/2in Bottom 10 5/8in
Width: 2.1in
Height: 2.38
Rails: 1913 spec rail with proper T-marks
Inside diameter: 1.37
Rails: 1913 spec rail with proper T-marks
Fasteners: grade 8 bolts phosphate finished
MADE IN USA

http://img.photobucket.com/albums/v503/AR15forme/Centurion%20Arms/IMG_4227.jpg (http://smg.photobucket.com/user/AR15forme/media/Centurion%20Arms/IMG_4227.jpg.html)

Since my existing upper assembly had been equipped with the standard handgaurds, a few parts had to go. This included the delta ring, weld spring, snap ring, front sling swivel and handguard cap. If you don't know what these parts are and aren't comfortable destroying them with a Dremmel tool, you might consider having an armorer or gunsmith do the installation for you. The gas tube has to be removed and reinstalled as well. Mine was glued in place with carbon, but some Kroil penetrating oil and a vice took care of it.

http://img.photobucket.com/albums/v503/AR15forme/Centurion%20Arms/IMG_4235.jpg (http://smg.photobucket.com/user/AR15forme/media/Centurion%20Arms/IMG_4235.jpg.html)

The rail system consists of an upper and lower half that wrap around the remaining barrel nut.

http://img.photobucket.com/albums/v503/AR15forme/Centurion%20Arms/IMG_4223.jpg (http://smg.photobucket.com/user/AR15forme/media/Centurion%20Arms/IMG_4223.jpg.html)

Installation at this point is as simple as could be. The upper and lower sections are positioned over the teeth of the barrel nut and the two halves are snapped together.

http://img.photobucket.com/albums/v503/AR15forme/Centurion%20Arms/IMG_4239.jpg (http://smg.photobucket.com/user/AR15forme/media/Centurion%20Arms/IMG_4239.jpg.html)

Next, the four cap screws over the barrel nut are snugged down. Then, the two domed cap screws toward the front sides are snugged down. Thread locking compound is not required, nor is a lot of torque needed, due to the use of helicoil inserts.

http://img.photobucket.com/albums/v503/AR15forme/Centurion%20Arms/IMG_4240.jpg (http://smg.photobucket.com/user/AR15forme/media/Centurion%20Arms/IMG_4240.jpg.html)

Front and rear quick disconnect (QD) sockets are machined into the right and left sides.

http://img.photobucket.com/albums/v503/AR15forme/Centurion%20Arms/IMG_4252.jpg (http://smg.photobucket.com/user/AR15forme/media/Centurion%20Arms/IMG_4252.jpg.html)

The front bottom of the rail is relieved to allow access to the bayonet lug. More on this in a bit.

http://img.photobucket.com/albums/v503/AR15forme/Centurion%20Arms/IMG_4258.jpg (http://smg.photobucket.com/user/AR15forme/media/Centurion%20Arms/IMG_4258.jpg.html)

The CNC machine work was flawless, as was the finish. The 1913 spec rails are all numbered.

http://img.photobucket.com/albums/v503/AR15forme/Centurion%20Arms/IMG_4250.jpg (http://smg.photobucket.com/user/AR15forme/media/Centurion%20Arms/IMG_4250.jpg.html)

Just a reminded when changing anything involving the barrel; live fire to verify zero. In this case, the point of impact shifted over six inches as 50 yards.

http://img.photobucket.com/albums/v503/AR15forme/Centurion%20Arms/IMG_4312.jpg (http://smg.photobucket.com/user/AR15forme/media/Centurion%20Arms/IMG_4312.jpg.html)

So what's the consensus on the rail? I like it! While the cost of $320 (retail) isn't exactly minimal, you typically get what you pay for with parts requiring this level of machine work and it's similar in price to those from other quality companies. The only bobble I experienced was with the bayonet lug contacting the right edge of the bottom rail. This creates an unwanted point of contact and has the potential to affect the accuracy. I've removed and reinstalled the rail once, with the same results. When I get some free time I'll be looking to address this.

http://img.photobucket.com/albums/v503/AR15forme/Centurion%20Arms/IMG_4373.jpg (http://smg.photobucket.com/user/AR15forme/media/Centurion%20Arms/IMG_4373.jpg.html)