SCHMID MIL-SPEC HARDENED STEEL BLACK OXIDE RECEIVER EXTENSION CASTLE NUT is a small part that does serious work on an AR build. This mil-spec receiver extension nut is made to secure the receiver extension and lock plate in place on an adjustable-stock AR-15 setup, giving the lower receiver assembly the proper retention it needs where it counts.

Schmid’s mil-spec version is built from hardened steel and finished in black oxide, giving you a tougher and more purpose-built part than bargain-bin hardware that cuts corners on material or finish. On a hard-use rifle, that matters. A castle nut takes real torque, and it needs to hold up when the stock assembly is properly installed and staked.

This version also includes staking cuts, which is one of the details serious builders look for. Those cuts give you the proper surface for staking the end plate into the nut after installation, helping the assembly resist loosening over time under recoil, handling, transport, and general hard use. It is a simple part, but it is one of those places where using a proper mil-spec component is just good judgment.

If you are finishing out a lower, replacing worn hardware, or building an AR the right way from the start, the SCHMID MIL-SPEC HARDENED STEEL BLACK OXIDE RECEIVER EXTENSION CASTLE NUT is a clean, dependable choice backed by a respected OEM name in the AR parts world.

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