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If you are reading this right now, you are likely at the point in your AR build where you are securing the buffer tube to the lower receiver. You’ve either decided to take the traditional route of securing the castle nut by staking it, or you’re trying to figure out if staking is right for you.
This guide will show you step-by-step how to stake a castle nut, but if you are still deciding “to stake” or “not to stake”, this guide also details why staking is highly recommended, but not always the best route and some alternatives.
Table of Contents
AR-15 Castle Nut Staking
What is a Castle Nut on AR-15?
A castle nut is a locking device that resists vibration [1]. It gets its name because notches are cut in one side resembling the parapet of a castle. The purpose of a castle nut is to lock parts together securely so they don’t come apart during use. An AR-15 castle nut locks the rifle’s buffer tube to the lower receiver.
Why do you stake the castle nut on AR-15?
You stake the castle nut to secure the buffer tube to the receiver endplate to prevent the parts from coming loose. If you don’t stake a castle nut, vibrations from regular operation can cause the nut to back out over time allowing the receiver endplate to come loose from the buffer tube.
The castle nut should be staked, especially if your firearm is going to be in regular use, like a competition or duty weapon. It’s good practice for any AR if you don’t expect to be changing out parts. Staking a castle nut is not complicated and takes most people less than 5 minutes to do. If you are not confident with your skills, send it to a gunsmith.
Although it’s the traditional way and some may tell you that you absolutely have to, there are times you may not want to stake the castle nut on your gun. If you regularly change parts on your AR, you may forego castle nut staking because each time you change a part, you have to break the stake.
A staked castle nut permanently changes the appearance of a weapon, making it a “no go” for some. While that is true, the security of knowing your weapon is reliable and will remain fully functional is more than enough to offset the change in appearance of your gun.
Alternatives To Staking A Castle Nut
If you prefer not to stake the castle nut in your AR-15 build, you have other options.
Do Nothing
The simplest option is to tighten the castle nut to the correct torque and stop there. No special tools or equipment are required, though a castle nut wrench makes it a lot easier and reduces the chance of marring the gun. This approach is easy and the appearance of your gun won’t be changed. But, if you go this route, you have to be vigilant about checking the castle nut and tightening it when needed.
Related: Armorer’s Wrench Reviews
Use a Less Permanent Solution
Some manufacturers have created some options that are more cosmetically appealing and easier to install and remove should you need to change your set up. The drawback is that these can be more expensive than the standard options and you won’t have the traditional look that you get from a staked castle nut. Also, options like these come in a set with both the castle nut and endplate.
Primary Weapon Systems Ratchet Lock Castle Nut and End Plate set uses a pin and detent to ratchet the castle nut down.
Fortis Manufacturing created a locking lever designed to seat itself into place without the need for staking the end plate.
Strike Industries created the anti-rotation castle nut and end plate with a built-in anti-rotate QD socket. Instead of staking, this setup uses a set screw to secure the castle nut to the endplate.
Strike Industries also offers their enhanced castle nut and extended end plate set which is easily installed with pin and detent using the set screw. They lengthened the castle nut to match the extended end, providing additional support of the receiver extension’s threaded area.
A Word About Loctite
You have probably seen a castle nut attached to the buffer tube with Loctite. While this approach does a great job of keeping the castle nut secured to the buffer tube, it does little to keep the buffer tube from backing out of the receiver. That is partially due to the vibration from operating the firearm, but Loctite may break down over time from exposure to lubricating and cleaning agents. Using Loctite is not something we recommend.
How to Stake A Castle Nut
A castle nut is staked by using a punch and hammer to spread some of the metal from the endplate into one or two of the castle nut notches. The steps below will walk you through the process in detail.
Step 1. Gather Your Tools
Bench Vise
Lower Receiver Vise Block
Center Punch (pointed or square tip)
Ball-peen or cross-peen hammer
Step 2. Set up Your Workspace
If your firearm is assembled, make sure the firearm is unloaded! Remove the upper receiver from the lower receiver. Securely position the lower receiver in the vise block.
Step 3. Stake the Castle Nut
Position the center punch on the middle of the endplate in line with one of the staking notches on the castle nut.
Put downward pressure on the punch and hold it straight out from the endplate. Gently tap the punch with the hammer until an indentation is created. When you are confident that the tip of the punch can rest in the indentation without slipping, strike the punch harder, but keep each strike controlled to ensure the punch doesn’t slip.
Stop when a good amount of metal from the endplate is spread into the notch of the castle nut. It doesn’t need to fill the notch, but make sure it’s not too shallow. Repeat the steps to stake a second notch.
FAQS
No, you do not need a gunsmith to stake a castle nut as long as you have the right tools to do it. There are various videos shown on YouTube on how to stake a castle nut for you to use as a guide.
If you over-tighten a castle nut, this may stretch bolts over its limits, or it could strip threaded fasteners. This can loosen nuts or crack it or, worst, break the bolt and nuts. Once this happens, it will have an uneven flange load that is no longer effective. The worst thing you will see is a joint failure where blowout pressure or hydrostatic force will increase significantly.
