Forward Controls Design likes castle nuts that can be staked to prevent them from rotating loose on the receiver extension and causing malfunctions. Army manual calls for the castle nut to be staked in two places. While Forward Controls Design is not in the "more is better, bigger is better" camp, there are times less is not more.
The TDP spec castle nut is a simple and robust fastener that is almost perfect for the job it is tasked to perform. Over the years, users have consistently come up with two minor gripes, first is its staking notches seem rather shallow and short, second is many do not 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.
Forward Controls' castle nut is based on the TDP spec castle nut, with a few changes:
1. 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.
2. Number of staking notches increased from 3 to 4, spaced equally on the castle nut. The castle nut is to be staked in two places. FCD is not advocating staking in more than two places. Forward Controls' castle nut'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.
3. 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 FCD's opinion that a castle nut should be staked per TM. Forward Controls' castle nut's longer and deeper notch reinforces the belief, that once installed and staked, it will not loosen without the user's deliberate action. FCD loves the idea of quick detach, but feels that some things on an AR are meant to stay put, and considerable effort was made to ensure that by the original designers. Forward Controls' castle nut is a continuation and evolution in that direction. Forward Controls' castle nut is machined from billet 4140 PH steel and black nitrided.
For complete and current information on this item please see the manufacturer's website.
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