FORWARD CONTROLS DESIGN
CN5F A5 Castle Nut
The CN5F is an extended version of the FCD CNF castle nut, made specifically for the VLTOR A5 system. It is 0.1 inches longer, which is as long as a castle nut can be made while keeping backward compatibility and still letting the stock fully collapse on the VLTOR RE-A5 and the FCD RE5F.
Before You Order
This is an A5 castle nut. It will physically work on a standard TDP length receiver extension, but the extra length will prevent a carbine stock from fully collapsing. If you are building a standard carbine, use the CNF instead.
On A5 tubes, the CN5F lets even the longest carbine stocks fully collapse on the RE-A5 and RE5F. Note that not every stock fully collapses on every A5 compatible receiver extension regardless of castle nut.
Why the Extra Length
The CN5F covers as much of the receiver extension's threaded area as possible. It could have been made longer, but past a point it runs into timing problems with some receiver extensions when installing the castle nut and end plate. The 0.1 inch is the practical limit.
What Else Changed From TDP Spec
A castle nut that rotates loose on the receiver extension causes malfunctions. The TDP castle nut does its job well, but its staking notches are shallow and short, and the wrench notches are sharp enough to be unpleasant when rotating the nut toward the end plate by hand. Aside from length, the CN5F carries the same fixes as the CNF:
- Staking notch angle changed from 45 to 30 degrees, producing notches 25% longer and deeper than TDP spec
- Staking notches increased from 3 to 4, spaced equally. The nut is still staked in two places, but 3 notches are visible at all times, giving more location options
- Coarse serrations on the wrench side to make rotating the nut toward the end plate easier during install
A castle nut should be staked per the TM. The longer, deeper notches mean that once installed and staked, it will not loosen without deliberate action. Quick detach has its place, but some things on an AR are meant to stay put.
Completing The Build
Pair it with an A5 length receiver extension, either the VLTOR RE-A5 or the FCD RE5F, plus an end plate: the ESF-H with three QD sling sockets or the ESF-H1 with a single rear socket.
Torquing requires a proper wrench. End plates with side facing QD sockets can block one of the three lugs on a conventional castle nut wrench, which the FCD JCW joint castle nut wrench solves with its two lug end.
Or configure a complete A5 setup with our A5 builder kit.
What's Included
1x Forward Controls Design CN5F A5 Castle Nut in your selected finish
Specifications
- Billet machined 4140 PH steel
- Available in black nitride, Cerakote FDE, and Cerakote ODG
- 0.1 inches longer than TDP spec
- 4 staking notches, 25% longer than TDP spec
- Coarse wrench-side serrations
- Designed for the VLTOR A5 system, RE-A5 and RE5F
- Not recommended on standard carbine receiver extensions
- Made in USA
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