The GunTec USA Extreme Duty Castle Nut (brand part no. CASTLE-EXD) is a wide, heavy-duty castle nut built for AR-15 buffer tube installations that demand extra strength. Made in the USA from steel and finished in a durable nitride coating, it fits both Mil-Spec and commercial buffer tubes, making it a drop-in upgrade regardless of platform. Its skeletonized, extended design gives more surface area to grip during installation while shaving unnecessary bulk, and the enhanced profile is built specifically for extreme strength and durability over a standard castle nut. It is a solid pick for builders who want a tougher, more secure buffer tube lock nut on a hard-use rifle.

Key Specifications

• Machined from steel for extra strength over a standard castle nut.
• Finished with a durable nitride coating for corrosion and wear resistance.
• Fits both Mil-Spec and commercial buffer tubes.
• Features a skeletonized, extended design for a larger grip surface during installation.
• Built in a wide, heavy-duty black profile for extra strength.
• Manufactured in the USA to GunTec’s enhanced-strength specification.

Frequently Asked Questions

Does this fit a commercial buffer tube? Yes, it fits both Mil-Spec and commercial buffer tubes.

What finish does this castle nut have? It is finished with a durable nitride coating over steel.

Buy the GunTec USA Extreme Duty Castle Nut

Lock down your buffer tube with a stronger, easier-to-grip nut from GunTec USA. Browse more build components in our gun parts kits category, and order it from our Lubbock, Texas gun shop for fast shipping.