I have a Sig 556R and have read that it’d be a good idea to Loctite the top picatinny rail on the receiver. I haven’t done it yet but was wondering if there is anything that the Loctite could drip down into and seize up, like the bolt carrier or such, i.e. does the screw hole go all the way down into the inside of the receiver?
Have you taken the rifle apart to see whats underneath from the inside?
I put locktite on my 556r to keep the rail from coming loose. Do it and you will be fine.