To clarify my point that the receiver plate does nothing other than allow you to retain a spring and do a staking job, you could thread the take down pin spring hole and put a screw in it and put no end plate on the rifle and either stake the receiver itself into the castle nut or even put a split ring lock washer in front of the castle nut for security and even loctite the RE extension into the receiver if you wanted. But because the ideal way is to just stake the castle nut and use an end plate to retain the spring, steel is stronger for the staking, but as KAC has shown with the newer SR15 RE nut without staking it (bc it isn't a "castle" nut) aluminum could stake it securely enough with proper torque value on the castle but itself.

