Fortis Castle Nut, Black, Anodized Finish, Mil Spec
Fortis Manufacturing
Overview
The Fortis Castle Nut is a standard type castle nut finished in a hardcoat anodized black, providing durability and a sleek appearance for your AR-15 build. This component securely fastens the buffer tube to the lower receiver, ensuring proper alignment and function of the recoil system. It’s commonly found in builds that feature a mid-length gas system chambered in 5.56 NATO, making it a reliable choice for those configurations.
Specifications
Build history on GunPartPicker
Builders on GunPartPicker first added the Fortis Castle Nut, Black, Anodized Finish, Mil Spec to a build in February 2026.
Availability is good: it was in stock at one retailer or another nearly every day in August 2026, and today all 4 retailers we track have it in stock. Prices barely moved in August 2026, holding around $11.35, so there haven't been real sales lately. Buying today, the lowest price is $11.35 at Optics Planet, which matches the best price we saw in August.
Updated · from real builds on GunPartPicker · Prices checked · refreshed daily across 10+ retailers
Builds Featuring This Part
See all 4 →Builds in the community that include the Fortis Castle Nut, Black, Anodized Finish, Mil Spec
| Build | Parts | Total |
|---|---|---|
 | 13 | $744.91 |
 | 21 | $801.17 |
 | 24 | $820.92 |
 | 23 | $994.79 |
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