Forward Controls Design CN5F For A5 Systems (Castle Nut, A5, Forward Controls)

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CN5F (Castle Nut, A5, Forward Controls) is an extended version of CNF we’ve been making since 2018.  CN5F is designed specifically for the superb Vltor A5 system, CN5F is 0.1″ longer, and is as long as we can make a castle nut while ensuring backward compatibility, and the stock’s ability to fully collapse on Vltor’s RE-A5 and our RE5F.  Note: not all stocks will fully collapse on A5 compatible REs.   For more information on the differences between RE-A5, RE5F and RE10/A5SR, please follow this link: https://www.forwardcontrolsdesign.com/Vltor-RE-A5-vs-RE10-A5SR_ep_78-1.html
CN5F aims to cover as much of the threaded area of a receiver extension (RE) as possible.  It could be made longer, but it will run into backward compatibility issues with some REs’ timing when installing the castle nut and end plate on the RE.  CN5F is made specifically for the Vltor A5 system, and it will allow even the longest carbine stocks to fully collapse on RE-A5 and our RE5F.  While CN5F will also work on standard TDP spec length RE, the additional length of the castle nut will prevent the carbine stock to fully collapse.

Other than its length, CN5F shares common features with its smaller brother, CNF.

The TDP spec castle nut is a simple and robust fastener that is almost perfect for the job it’s tasked to perform.  Over the years, we’ve consistently come up with two minor gripes, first is its staking notches seem rather shallow and short, second is we don’t enjoy using the castle nut’s wrench notches as serrations (our fingers invariably find their way to these sharp cutouts) to rotate it towards to the end plate while installing it.CN5F (Castle Nut, Forward Controls) is based on the TDP spec castle nut, with couple of changes:

1. 0.1″ longer.
2. Staking notches angle changed from 45 to 30 degrees, this results in longer (25% longer than TDP spec) and deeper notches than found on TDP castle nuts.
3. Number of staking notches increased from 3 to 4, spaced equally on the CNF.  The castle nut is to be staked in two places, we’re not advocating staking in more than two places, CNF’s 4 staking notches mean that, at all times, 3 will be visible and available for staking, it simply gives the user more staking location options.
4. Coarse serrations on the wrench side of the nut, a single use feature to make it easier while rotating the CNF towards the end plate.

It is our opinion that a castle nut should be staked per TM, CNF’s and CN5F’s longer and deeper notch reinforces the belief, that once installed and staked, it will not loosen without the user’s deliberate action.  We like the idea of quick detach, but some things on an AR are meant to stay put, and considerable effort was made to ensure that by the original designers.  CNF  and CN5F are a continuation and evolution in that direction.

CN5F is billet machined in 4140 PH steel, and black nitrided (Cerakoted FDE, OD green, and burnt bronze also available).  As with everything Forward Controls Design produces, it is proudly made in the USA.

We’d like to thank Ash Hess for letting us use parts of the Army/Air Force / Navy TM for CNF’s installation instructions, on the back of the card.

Additional information

Weight 1 oz
Dimensions 3 × 2 × 1 in
Color / Finish

QPQ Black, Cerakote FDE, Cerakote OD Green

25 reviews for Forward Controls Design CN5F For A5 Systems (Castle Nut, A5, Forward Controls)

  1. Joe Seifert (verified owner)

    As always solid product from FCD and awesome customer service from BTO

  2. Mike (verified owner)

    The extra length of the FCD castle nut is nice, and aesthetically pleasing. However the function of these is also fantastic — it is a minor thing, but the improved staking area makes a real difference. If you’re investing in a VLTOR setup go ahead and grab one of these to complete the package in the best way possible. Simple but a nice improvement above stock milspec parts.

  3. ericneth (verified owner)

    All my builds get an FCD castle nut. Really like the extra length of the CN5F on my A5 buffer extension. Easy to install with the way the notches are cut into the castle nut. Can’t go wrong with FCD product.

  4. Justin (verified owner)

    Cant go wrong with any FCD products.

  5. Nick B (verified owner)

    Coupled with A5 system, like peanut butter and jelly.

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