AT3™ Castle Nut for AR-15 Buffer Tubes – 10 Colors Available

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Secure Your AR15 Buffer Assembly with a Steel Castle Nut

This steel castle nut is an essential piece of an AR15 buffer tube/stock assembly.  With standard cuts for use with armorer’s wrench, and smaller cuts for “staking” the castle nut and endplate for a secure hold, this part does everything it should at a good price.  If you’re in need of a spare for a new build or replacing a damaged component, this one is right for you.  You can also add a little more color to your black rifle with with your choice of Cerakote™ finish. You can choose from FDE, ODG, Pink, Gray, Blue, Red, Burnt Bronze, Tungsten, and Titanium.


  • Material: Steel
  • Finish
    • Black: Phosphate
    • Flat Dark Earth: H-267 Magpul® Flat Dark Earth
    • OD Green: H-232 Magpul® OD Green
    • Gray: H-188 Magpul® Stealth Grey
    • Pink: H-224 SIG™ Pink
    • Red: H-167 USMC Red
    • Blue: H-171 NRA Blue
    • Burnt Bronze: H-148 Burnt Bronze
    • Tungsten: H-237 Tungsten
    • Titanium: H-170 Titanium
  • Thread: Mil-Spec
  • Compatible with armorer’s wrench

Products available on this page:

Have Questions About this Product?

The AT3 Tactical store has a 90 day no-hassle return policy for products in good condition. You can view the full details of our return policy here.

If you encounter an issue or defect with a product after 90 days of your purchase, you can refer to the manufacturer for a warranty claim. Their policies are below.

AT3 Lifetime Warranty Logo

All AT3 Tactical Brand Products carry a lifetime warranty against manufacturer’s defects.

This includes AT3 Red Dot SightsHandguardsIron Sights, and any other product that carries the “AT3 Tactical” or “AT3™” name. For other brands (ex. Magpul or Troy), please refer to the manufacturer’s warranty policy.

In the event that your AT3™ product becomes unusable, we will repair or replace the product at no charge to you.

If we cannot repair your product, we will replace it with a product in perfect working order of equal or better physical condition. The warranty is fully transferable, but we may require information about the original purchase to validate the authenticity of the product.

If your product is in need of warranty service, please contact AT3 Tactical to start the process

Our contact info is available here. To expedite processing, please provide your order information and description of the defect.

Please note: The AT3 Lifetime Warranty does not cover loss, theft, intentional damage or cosmetic damage that doesn’t affect the performance of the product.

Customer Reviews

Based on 89 reviews
Eliseo Melendez
Castle Nut

Looks great, it was exactly what I was looking for. Thank you.

Thanks for sharing your feedback! We're glad you're satisfied with your purchase.

Darryl M
AT3 Castle nut in Burnt Bronze

This nut not only secures my QD end plate, but it looks FLY on my BB 223 Wylde build!

Thanks for sharing your feedback! We're glad you're satisfied with your purchase.

Roy E Hooker
Awesome FDE finish

Perfect FDE to my orther FDE and Magpul, Aero FDE, definitely a premium part for awesome price, AT3 is not messing around. Will buy from them again . Don’t forget fast shipping. 3 days after shipped. That’s fast shipping Hooah!!

Thanks for sharing your feedback! We're glad you're satisfied with your purchase.

MarQ Patriot

I was purchasing parts to finish a lower(have not started it yet)and future build. Castle nuts are castle nuts, right? Not really, I did purchase this for the price and cause it was in stock(lol)but I must say it is very good quality even at $4.... No burs on the edges, wrench cuts and punch grooves are precise and clean. It seams to be a solid part and I’m sure it will do the job... Thank you, AT3...

Thanks for sharing your feedback! We're glad you're satisfied with your purchase. Cheers!

Dave Renfroe
Castle Nut

Just a plan castle nut at a normal price but with all these want to be people trying to build AR's because of covad you cant find anything local. AT3 is always my place to go when I cant find it local and they are the place I go because they beat most local prices on high end parts. Shipping is just sick, Parts are always on time if not earlier. AT3 Rocks!!!!!