Forget what you just read on Reddit and Facebook. There are plenty of wrong ways to stake an AR-15's castle nut. Then there's Caleb's Way, which he's going to demonstrate for us today. The castle nut threads onto the receiver extension (aka buffer tube) and locks the extension to the receiver. It's called a "castle nut" because of the evenly spaced wrench notches that make it look like the top of a medieval castle's tower. You stake the castle nut to the receiver endplate to prevent it from backing out, which in turn prevents the receiver extension from working loose.
Caleb demonstrates with a Geissele buffer tube, Bravo Company endplate, and a Forward Controls Design Castle Nut FCD. You'll need a bench vise, lower receiver vise block, cross-peen hammer, and a center punch - pointed tip or square tip is fine. Do not use a woodworker's countersink punch! Before he begins, Caleb shows us an example of how NOT to stake the castle nut: too shallow, with mere surface damage to the nut and endplate. You've gotta move some metal to do a proper staking job!
There are three small, shallow notches on the side of the castle nut that faces the rear of the receiver. Position the punch with its tip covering about half the depth of the endplate directly opposite a notch. Hold the punch so it stands straight out from the side of the endplate - don't angle it. Lightly tap it several times with the hammer to start making an indent in the endplate. Once you've made a nice indent to keep the tip of the punch from slipping, you can apply harder hammer strikes, but DO NOT whale on it!
When you're done, you should have a neat, circular dimple in the endplate, with a good bit of metal smooshed (technical term) into the notch in the castle nut. For an extra-secure installation, stake one of the other two notches in the castle nut. (You don't have to do all three.) That castle nut is NOT coming loose without your help!
Is staking really necessary? Find out in our earlier video "Smyth Busters: Does an AR-15 Castle Nut Have To Be Staked?"
Get the details on FCD's upgraded castle nut: "Product Spotlight: Forward Controls CNF Castle Nut"
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