My take:I generally put something on threads so its not dry,unlubricated steel on steel.(unless the instructions say so)
These days,I usually put never-seize on barrel threads,but,accepting I will have created a monster if I want to take it apart,I have locktighted some barrels .I am careful with my thread forms and fit to minimal clearances on barrels I thread,etc.I generally true all faces,too.I torqiue a barrel tight enough it wont unscrew,but I do not get crazy about it.Many benchresters use minimal torque on their barrels.
My theory,I wanted to fill in all the clearance and make it a dead joint.Agreed,with fresh,precision threads its probably not necessary,but on a 80 or 100 year old milsurp set of threads,they won't be perfect.
I think that is why Rem loc-tites the bbls in.Its to take out any flex room in the joint...Its not about the barrel unscrewing.
On screws,no need to make more trouble than necessary,many screws don't need it,but on scope mounting,I'll put a touch of sleeve retainer between the base and the receiver as a bedding compound. There are few mechanical fits that are perfect.I use blue on the base screws.
Scope base screws are small for the job they do.They do not engage a lot of depth of thread length.There must be some thread clearance.You hang a big heavy scope on those screws and shock them with recoil,I think of loosening a fence post by working it back and forth.
That is also hard on the female threads in the receiver.So,for me,the loctite is not so much about the screw rotating to unscrew,it stabilizes the joint,removes wiggle room.
Oh,if I ever do need to pull one of those barrels back out,I'm thinking a soak in a pan of hot peanut oil should get it up to temp ,
To the original question,There are few applications for loc-tite on an AR.
Yes,there are marginally designed aftermarket parts,but as the OP pointed out,there are alternate parts with better designs.
Last edited by HiBC; June 20, 2012 at 10:34 AM.