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Forward Controls Design CN5F Castle Nut for A5 Buffer Kits


The CN5F castle nut is made for VLTOR A5 buffer systems and is slightly longer than the CNF (.1”) to make sure that the adjustable stock can fully close. Since it’s longer, it will also cover up most of the threaded portion of your buffer tube and due to it’s length when it’s used with standard buffer tubes, the stock probably won’t collapse all the way to close the gap with the castle nut. Forward Controls Design CN5F is longer than the CNF castle nut but it shares all of the same improvements.


  • For A5 Length Receiver Extensions
  • 4140 PH Steel construction
  • 25% longer staking notches
  • Additional notch added
  • Coarse serrations for easy installation

The original MIL-SPEC castle nut is a hard product to improve upon, but Forward Controls Design has proven it is not impossible. The CNF is based on the original technical data package specification for the castle nut but does offer several improvements. Deeper staking notches make for much more secure staking. Even installation is improved with the coarse serrations making threading it down to the endplate easier and more comfortable.

Military specifications require castle nuts to be staked in two locations to ensure the castle nut and buffer tube will not loosen without deliberate action, and FCD believes this is one of those points where less is definitely not more. Traditional MIL-SPEC castle nuts have 3 staking notches, the CNF features 4, ensuring at any time three are available to be used. Each notch has also been upgraded to a deep, 30-degree cut, making them 25% longer than MIL-SPEC to ensure enough material can be staked into the notch for secure installation. To make threading the castle against the end plate even easier, the outer edge features coarse serrations.

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