I might give that a try, ric. Another DPMS factory rifle I had, an LR-308, had the barrel nut torqued on so tight I had to use heat in addition to my heavy duty strap wrench when I removed it to sandblast it for a matte finish. However, I don't recall the barrel extension being a tight fit in the upper, so could very well be that this LR-6.5 could benefit from the blue loctite treatment.
Oh, and Bob, a question regarding your gas tube centering method. Does centering the tube using this method typically leave the gas block at top dead center? I know the block vent hole is large enough to accomodate some some side-to-side slop and still handle the full gas volume, but I was curious if the block had a rail if it typically aligned with the rail in the upper. I suppose it's a moot point for me because I'm running glass only on this gun with no back up sights.