CN5F is designed specifically for the superb Vltor A5 system, CN5F is 0.1″ longer, and is as long as they 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.

(11 customer reviews)

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CN5F (Castle Nut, Forward Controls) is based on the TDP spec castle nut, with couple of changes:

  •  0.1″ longer.
  • 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.
  • 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.
  • 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.
  • 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.

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  1. frosty (verified owner)

    Fit and finish is excellent. Almost completely covers the threads on my A5 receiver extension.

  2. davidwzimmer (verified owner)

    When you start using Forward Controls Design parts on builds, it’s really hard to go back to anything else. This A5 length castle nut is a must have when building an A5 buffer system.

  3. matthew.roy76 (verified owner)

    Forward Control Designs makes innovative and high quality parts: love the quality machining, fit, and finish. Used w/ carbine buffer tube and Fortis QD End Plate and threads are completely covered. Couldn’t be happier.

  4. ajero0013 (verified owner)

    Perfect for the A5 buffer system. Going to snag another in ODG

  5. Wecameforyourkings (verified owner)

    This is definitely better than the regular FCD castle nut if you are running a VLTOR A5 tube!

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