Anderson Manufacturing AR-15 Buffer Tube Castle Nut

Manufactured by Anderson Manufacturing
SKU: AM-26
MPN: AM-26
Manufactured by Anderson Manufacturing
39 Reviews

In Stock

Standard orders will ship out in 1 business day (M-F) if ordered by 3:30 pm CST. FFL orders will ship within 5 business days or less as long as we have the information for the transfer destination. NFA items will take longer to ship and are dependent upon ATF processing times.

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The Anderson Manufacturing MIL-SPEC AR15 castle nut is built from high quality steel and Manganese Phosphate coated. A Mil-Spec AR-15 castle nut might be an after-thought to most AR builders but it is an essential component for keeping your rifle running reliably. The castle nut simply slides over the receiver extension/buffer tube and is screwed on to secure the entire buffer and stock system to the lower receiver. This connection between the buffer system and receiver is generally regarded as one of the weak spots on the AR platform and this Mil-Spec castle nut will ensure your buffer tube is solidly attached for thousands of rounds. Especially if you stake the end plate resulting in a mechanical connection between the two pieces of metal and preventing the castle nut from loosening over time.

  • Mil-Spec dimensions for AR-15 buffer tubes
  • Manganese Phosphate finish
  • Wrench cutouts for installation
  • Cutout for staking
  • Manufactured in the United States

The AR-15 castle nut gets its name from the castle turret like cutouts that allow a castle nut wrench to slide in and allow you to torque the castle nut down. In general, it is recommended that you torque your castle nut to 40 ft/lbs and do not use thread locker on these threads as that will give you inaccurate torque measurements. The wrench cutouts will face away from the receiver and a smaller cutout will be on the side that faces the receiver and sits flush with the end plate. Using a hardened punch, place the tip on the edge of the end plate and lightly tap it with a hammer to deform the metal into the cutout on the castle nut. This will prevent your castle nut from backing off the threads over time while still allowing you to use a wrench and remove it for maintenance if necessary.
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BrandAnderson Manufacturing
Manufacturer.Anderson Manufacturing
California Prop 65 warning

 WARNING: This product can expose you to chemicals, which are known to the State of California to cause Cancer and Reproductive Harm. For more information go to

Ratings & Reviews

39 reviews


Excellent product


Easy installation

good one


What can I say? It's a castle nut, it does what a castle nut is supposed to do.



Should have checked the reviews. All six of mine exhibited minor rust around the edges. don't mine the thin finish but this rust would not easily rub off. Looks bad especially when you are building for someone else.

Came with Rust


When I first got it I thought it did look a little rough. I tried to clean it up only to realize it had rusted already.



Got this product today and the edges are all rusted. Cant really complain as it's 4 dollars but still would like to recieve my parts in good condition free of rust and scratches

Great deal

by -

Works as expected. Anderson is reliable.

Nice Upgrade

by -

I ordered this part to go with a buffer tube on my newest build and I was amazed with it. it's a bit deeper then any other Castle Nut I have received in a kit. It looked good and was oiled but the oil was tacky and almost dried up on it. I give it 4 stars because I do like that it is deeper in depth and hides more of the threads then the usual nut. I did take away one star only because of the dried up oil that was hard to clean and the fact that it's a flat black coating. I will be using these for more of my future builds and may just replace all my others with this nut as it covers more threads and gives it a cleaner look. Over all I do recommend this product to any one looking for a replacement part on a new build.

Castle nut

by -

Basic castle nut. Does what it's supposed to.


by -

I was torqueing this down to 40ft/lb per spec and broke off a chunk at the edge of one of the cut outs before I hit 40. The description doesn't say if it's aluminum or steel, but I'm guessing aluminum. Seems otherwise intact but I will replace it with another brand that I know is steel.