Well, that’s settled. 
Definitely yes. I have come across too many instances of them backing out.
I hope you staked that bad boy by now. I just used up 3x the time it would take you to stake that castle nut reading this thread.
rock out with your stake out!
Does it have to be staked? I don’t know, there are other ways to secure as have been mentioned. What I do know is staking has never caused a problem so why not the extra insurance.
I did see a damaged lower a couple weeks ago that occurred when the castle nut loosened allowing a little play in “the buffer tube.” The buffer tube had been screwed in to a point where it just barely covered the buffer retainer. The buffer tube was not notched at 6 o’clock and would not turn in another full turn. While firing, when the buffer bottomed out in the tube, the the threads of the tube and receiver had just enough play to allow the buffer tube to move backwards. This released the buffer retaining pin. The pin popped up in front of the bolt carrier which, on its forward movement, struck the pin and egged out the receiver hole the buffer retaining pin and spring fit in.
Ok, that was a long story. The punch line is “stake the castle nut.” Also, notching the buffer tube at 6 o’clock and turning it in one more turn would have helped. This would serve two purposes. It insures the buffer retaining pin stays put and the buffer retaining pin will help prevent the buffer tube from turning should the castle nut come loose.
OK, stake it is. 
I have staked all of mine. I think it’s cheap insurance. I was at a gun show lately and was amazed at the amount of AR’s for sale that weren’t staked. I’d say 95% weren’t and there were literally hundreds there for sale. I’ve never seen a Rock River staked and Olympic Arms must make their own castle nuts because all the ones I saw for sell didn’t even have the notches in the nut to stake into. I put together a rifle for a buddy lately using all his supplied parts and he had some kind of end plate that had loops built into it. The damn thing must have been made from cast iron because I dulled my best punch on the thing trying to stake it and it all it did was knock the paint off the end plate. I guess loc-tite would be the only way to make sure it will stay secure. I guess he’ll find out sooner or later.
I’ve never seen a Rock River staked
They are using Loctite instead of staking.
and Olympic Arms must make their own castle nuts because all the ones I saw for sell didn’t even have the notches in the nut to stake into.
Yup. And they typically install them backwards.
YES. Have seen unstaked ones come loose with resultant problems. Good luck finding the spring and detent when they fall out.
Steak? Oh yes please! Knock it horns off, wipe its ass and put it on a plate.
Oh wait, what was the question again? 
I bought one from Horror Freight for $1.99.
As often as I use it (extremely rarely), it’s been entirely adequate.
Bimmer
And a non-spring loaded punch is even less. And then everyone has a hammer lying around somewhere.
No reason to not stake the castle nut (and the carrier key bolts). No reason whatsoever.
The DPMS castle nut I bought was the same way, no notches. That’s what started me replacing the few DPMS parts I was using. It’s better now.
I actually loaned a guy at work my stock wrench today because his Bushmaster stock loosened up on him. I guess I can add Bushmaster to the list of non end plate stakin’ bastards.
I am staking receiver nuts all the time. I’ve easily done hundreds of them.
On new Colt M4s, they are staked. So heavily that the endplate is pushed into the threads of the receiver tube. I love that part.
I use both the spring loaded and solid punch.
center punch the plate so your solid punch doesn’t skip off the part.
I use a fat punch, not a skinny one. Usually a reground old broken starrett punch. The point being tapered at a bit less than a 90 occluded.
When you center punch the plate, angle the punch slightly toward the nut. first punch vertical, then two more taps at the oblique angle. This displaces steel toward the staking recess.
Use the solid punch, hold at an angle to swedge the metal toward the recess. With the right shaped tool, you’ll get quick and easy stakes.
You can get two stakes on one nut. The third will never be in position. You really get the touch when using the ambi sling plates (that I fuggin hate).
Most importantly, degrease all the parts… and use some anti seize. Using loctite is cheap and retarded. The mentioned manufacturers do not surprise me.
No joke! I was test fitting the RE on a lower I was assembling for a friend, un-screwed it (not thinking about the spring and detent), said a few choice words and started the 45 minute search for the needle in the haystack/garage.
it’s easy if you follow the order of operations.
-Break the stakes (dremel wheel or bull strength)
(now this is important for saving your parts)
-place your left hand over the lower receiver, to trap the detent incase it flies. With your thumb of the same hand place pressure on the back of the receiver plate.
(the takedown pin should be in the open position to relieve pressure on the detent)
-while holding the plate, back the nut off with your right hand… give yourself space to work.
-carefully let pressure off of the end plate and tighten the tube 1/8 turn to allow you to remove the takedown detent spring.
-now spin the tube counter clockwise to remove it, your left hand will capture the buffer detent.
when reinstalling the parts, after degreasing and reapplying anti-seize…
-stack the nut and plate on the tube. Make sure they are facing the right directions
-tighten tube into receiver, being certain to capture the buffer detent. You will overtighten a partial turn so that you can fit the takedown spring past the endplate
-insert takedown spring. If need be, use a .025" feeler gauge to shim the spring in place while you rotate the endplate back into position.
-with your left hand, hold the plate in position (thumb) while covering the buffer detent.
- hand tighten the nut down till it is snug. Now you can go hands off for torquing. I don’t worry about torque spec’s. I simply tighten, then torque until I can stake at two points.
…already covered the staking part
BTW, its much easier when you remove the buffer and spring.
What anti-seize grease are you guys using when installing the extensions?
I don’t use grease between a CAR receiver extension but I do use a tiny bit of Brownells Action Lube Plus between a rifle or entry length extension and the receiver.
Thanks
I use the same.