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I grease the threads, tighten, loosen and do that 3x.  Then disassemble, degrease everything, assemble, tighten it down good with a wee bit of blue loc-tite at the 6 o'clock position in such a manner that an old fashioned soldering iron (the non-torch kind) can heat up the loc-tite enough to break it loose if I want to disassemble the unit later.

Tightening to GI spec is pretty tight, and staking the part requires grinding off the displaced metal if I want to change things later on.  So I don't like either torquing things that heavily, or staking.  So far, I have never had a castle nut loosen.

An alternative is to drill through the castle nut and tap a little Allen head screw that ends up in the space between the threads at the 6 o'clock position...again with the blue loc-tite.  That wasn't an original idea from me.  I had a very old nut that didn't even have the castle cut outs, and all it had was the Allen head screw to lock it in place.

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Agreed, that's possible, just scared me good when ATF guy showed up looking for an unregistered AR-15 SBR that someone said I had.  So, I kind of went full on prevention mode.  Mainly worried about that same cop pulling me over again when I an transporting one of my ARs and being sure it would be impossible for him to make a quick and easy parts swap "on the fly" since I strongly suspect it was him and I know he has something stuck in his craw about AR pistols and he thinks they should be considered SBRs.  That with the complaint made against me being that of unregistered SBR, that and my video humiliating him in court and showing him a perjurer and it being shortly after the ATF complaint was made.  Well, as I said, shame on me if he pulls the same thing twice and is successful.  He could do something else that I can't forsee but he sure ain't going to be able to pull same thing twice.  That also applies to a few Bicycle related things that are not gun related, he hates bicyclists, he hates gun-nuts, he really hates some who bicycles with a gun on them especially an AR, especially an AR pistol.  I am often most or all of the above.