I've never had a nut hit 70ft-lbs to line up. The most I can recall was a Citadel A1 barrel on an RRA A2 upper which lined up at 64ft-lbs, but the others have all been well below 50ft-lbs. The last two I did were a Colt socom barrel on colt M4 upper set at 36ft-lbs and the Daniel Defense M4 barrel I put on my Vltor MUR upper last night torqued at 41ft-lbs.
There might be some kind of relation between manufacturer tolerances to be found, but I've done nowhere near enough assemblies to figure them out.