Re: JP adjustable gas block
They are especially nice on AR-10 platform rifles. Adjusting the gas really helps control that big bolt from slamming around so much.
I have them on AR-15 platform rifles but open them all the way up and loctite the screw. I've been bitten a few times in matches with them getting out of adjustment, closing off the gas too much and stopping the rifle from running (just my experience)
John is right, color of loctite doesn't really matter, they all will break down with the heat generated from medium to high volume firing.