If he tried 2 scopes and a different mounts and it won't sight in, it leaves the boresighter. Guns and quality scopes don't go bad without damage, if neither is the case then it's the boresighter or the dumb dumb using it. I had a gunshop break a brand new scope when he ran out of adjustment but he seen that the scope had markings left that indicated it had 1 turn left and forced it to turn and broke the windage adjuster and a broke one of the lens on the inside.