Re: Shots going right
There's one other thing I can think of that's not shooter related.
It's the possibility of the scope being mounted off center to the bore. I know, I know, not likely on most rifles; but it's all I could think of, and this guy's leaving soon for a hunt.
This thought comes from one of my great uncles' Benchrest rifles that had the scope mounted 1" left of TDC (yes, on purpose). We could shoot the wings off flies with it at 100, but it took a ton of adjustment to get zero'd at 300. I can only assume that it would be ever increasing as distance got further. Not necessarily proportionally either...??
Just a thought, probably nothing.
Aim small = Miss small