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AR-15 Castle Nut | Mil-Spec, Enhanced & Anti-Rotation Nuts
AR-15 Castle Nut – Secure Your Buffer Tube with Confidence
🔧 Mil-Spec, Enhanced & Anti-Rotation Castle Nuts for AR-15 Builds
Your AR-15 build is only as strong as its weakest link. A high-quality AR-15 castle nut ensures your buffer tube stays locked down, your end plate remains properly aligned, and your rifle runs reliably under recoil and hard use. Whether you’re assembling a brand-new lower or replacing worn-out parts, choosing the right castle nut is essential for both performance and safety.
🧱 What Does a Castle Nut Do on an AR-15?
The castle nut threads onto your carbine buffer tube and locks your end plate against the lower receiver. This setup keeps the receiver extension (buffer tube) firmly in place and helps maintain alignment for your stock and buffer system.
If the castle nut loosens during use, it can cause cycling issues, stock wobble, or even safety problems—so a secure fit is critical.
🔩 Types of AR-15 Castle Nuts We Carry
🔹 Mil-Spec Castle Nuts
- Standard size, hardened steel
- Compatible with most AR-15 carbines
- Designed for proper staking
🔸 Enhanced & Lightweight Castle Nuts
- Anodized or coated for corrosion resistance
- Some feature notches for anti-rotation end plates
- Ideal for tactical and duty builds
🟢 Castle Nuts with Anti-Rotation Tabs
- Works with matching end plates
- Prevents the nut from backing out
- Excellent for hard-use rifles and duty-grade setups
🛠️ Choosing the Right Castle Nut
| Type | Best Use | Material | Features |
|---|---|---|---|
| Mil-Spec | Standard carbine builds | Steel | Basic, proven, stakeable |
| Enhanced | Custom or lightweight ARs | Aluminum/Steel | Coated, low profile, stylish |
| Anti-Rotation | Tactical / hard-use rigs | Steel/Coated | Locks with end plate tabs |
🧰 How to Install an AR-15 Castle Nut
- Slide on your end plate and thread the castle nut onto the buffer tube.
- Use an AR-15 armorer’s wrench to tighten the nut to ~40 ft-lbs.
- Stake the castle nut by deforming the end plate into the notches.
- Check for alignment and torque again after the first 100 rounds.
❓ Frequently Asked Questions
Q: Can I reuse a castle nut?
Technically yes, but it’s not ideal. Worn threads or improperly staked areas can cause loosening over time. For reliability, we recommend replacing it with a new one.
Q: What torque spec should I use?
Most builders use 38–42 ft-lbs of torque. Always follow your lower receiver or end plate manufacturer's guidelines if specified.
Q: Is staking required?
Yes, especially for defensive or duty rifles. Staking prevents the nut from backing off under vibration or recoil.
Q: Will this fit my AR-15?
All our castle nuts are made to mil-spec dimensions and will fit any standard AR-15 carbine buffer tube setup.
🛒 Shop AR-15 Castle Nuts Today
Don’t cut corners on one of your rifle’s most important components. Choose from our selection of mil-spec, enhanced, and anti-rotation AR-15 castle nuts—trusted by builders and professionals nationwide.