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Forward Controls Design
The Forward Controls Design A5 Castle Nut in Burnt Bronze is a precision-engineered receiver extension fastener built specifically for the Vltor A5 stock system. If you're running an A5-compatible setup and want a castle nut that actually addresses the real frustrations shooters face during installation and maintenance, FCD's CN5F is a thoughtful evolution of the standard TDP spec design—taller, smarter, and made to stay locked in place.
FCD spent real time thinking about what makes castle nut installation annoying: shallow staking notches that are hard to catch reliably, and sharp wrench serrations that dig into your fingers. The CN5F solves both. The staking notches are angled at 30 degrees instead of 45, making them 25 percent deeper and longer than standard, with four notches instead of three—giving you more reliable staking options while leaving three notches visible at all times. The wrench side features coarse serrations that make rotation toward the end plate smooth and pain-free. This nut is 0.1" longer than FCD's standard CNF, extending coverage of the threaded receiver extension while maintaining full backward compatibility with Vltor RE-A5 and FCD RE5F systems, allowing even longer carbine stocks to collapse fully.
Built from 4140 PH steel and finished in FCD's burnt bronze Cerakote, this castle nut is billet machined and made in the USA. At 0.51 ounces, it's a small component that makes a real difference in how your AR handles assembly and disassembly. Once properly installed and staked per the manual, it's designed to stay put—no rattle, no creep—until you deliberately remove it.
| Material | 4140 PH Steel |
| Finish | Burnt Bronze Cerakote |
| Weight | 0.51 oz |
| Design | Billet machined |
| Staking Notches | 4, 30-degree angle |
| Made in | USA |
The CN5F is designed specifically for Vltor A5 and FCD RE5F receiver extensions. It will allow even longer carbine stocks to fully collapse on these systems. It will also work on standard TDP spec length receiver extensions, though longer stocks may not fully collapse due to the nut's extended length.
The CN5F features four staking notches angled at 30 degrees instead of the standard 45 degrees, making them approximately 25 percent deeper and longer than TDP spec notches. This provides more reliable engagement and staking options, with three notches always visible for selection.
Yes, the CN5F will function on standard TDP spec receiver extensions, maintaining backward compatibility. However, the additional length means longer carbine stocks may not achieve full collapse. It's optimized for A5-compatible systems where the extra length is beneficial.
The CN5F is 0.1 inch longer than FCD's standard CNF model, designed to cover more of the threaded receiver extension while preserving compatibility with A5 and RE5F systems.
Forward Controls Design
The Forward Controls Design A5 Castle Nut in Burnt Bronze is a precision-engineered receiver extension fastener built specifically for the Vltor A5 stock system. If you're running an A5-compatible setup and want a castle nut that actually addresses the real frustrations shooters face during installation and maintenance, FCD's CN5F is a thoughtful evolution of the standard TDP spec design—taller, smarter, and made to stay locked in place.
FCD spent real time thinking about what makes castle nut installation annoying: shallow staking notches that are hard to catch reliably, and sharp wrench serrations that dig into your fingers. The CN5F solves both. The staking notches are angled at 30 degrees instead of 45, making them 25 percent deeper and longer than standard, with four notches instead of three—giving you more reliable staking options while leaving three notches visible at all times. The wrench side features coarse serrations that make rotation toward the end plate smooth and pain-free. This nut is 0.1" longer than FCD's standard CNF, extending coverage of the threaded receiver extension while maintaining full backward compatibility with Vltor RE-A5 and FCD RE5F systems, allowing even longer carbine stocks to collapse fully.
Built from 4140 PH steel and finished in FCD's burnt bronze Cerakote, this castle nut is billet machined and made in the USA. At 0.51 ounces, it's a small component that makes a real difference in how your AR handles assembly and disassembly. Once properly installed and staked per the manual, it's designed to stay put—no rattle, no creep—until you deliberately remove it.
| Material | 4140 PH Steel |
| Finish | Burnt Bronze Cerakote |
| Weight | 0.51 oz |
| Design | Billet machined |
| Staking Notches | 4, 30-degree angle |
| Made in | USA |
The CN5F is designed specifically for Vltor A5 and FCD RE5F receiver extensions. It will allow even longer carbine stocks to fully collapse on these systems. It will also work on standard TDP spec length receiver extensions, though longer stocks may not fully collapse due to the nut's extended length.
The CN5F features four staking notches angled at 30 degrees instead of the standard 45 degrees, making them approximately 25 percent deeper and longer than TDP spec notches. This provides more reliable engagement and staking options, with three notches always visible for selection.
Yes, the CN5F will function on standard TDP spec receiver extensions, maintaining backward compatibility. However, the additional length means longer carbine stocks may not achieve full collapse. It's optimized for A5-compatible systems where the extra length is beneficial.
The CN5F is 0.1 inch longer than FCD's standard CNF model, designed to cover more of the threaded receiver extension while preserving compatibility with A5 and RE5F systems.
