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Anderson Manufacturing AR-15 Buffer Tube Castle Nut

Manufactured by Anderson Manufacturing

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.

Features:

  • 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.