This Castle Nut for AR-15 is a direct-fit castle nut from Sons of Liberty Gun Works (brand part no. CASTLENUTMS), built for standard mil-spec-thread AR-15 buffer tube assemblies. The castle nut threads onto the buffer tube and locks against the receiver end plate to keep the tube from backing out under recoil. It’s a small but functionally important part of any AR-15 stock or brace installation.

Key Specifications

• Functions as the castle nut that locks the buffer tube against the receiver end plate.
• Threaded for mil-spec buffer tube diameter AR-15 builds.
• Sized as a direct-fit replacement for standard AR-15 pattern lowers.

Frequently Asked Questions

What does the castle nut do? It threads onto the buffer tube and locks against the receiver end plate to keep the tube from backing out under recoil.

What thread pattern is it built for? Standard mil-spec-thread AR-15 buffer tube assemblies.

Buy the Castle Nut for AR-15

Keep your buffer tube locked down with this Sons of Liberty Gun Works Castle Nut sized for mil-spec AR-15 builds. It ships fast from our Lubbock, Texas gun shop, and our small AR-15 parts selection has more small AR-15 parts.