Originally Posted by RobF
You of course checked the gun was level first?
Plumb or plum?
I have one of those little Hawke bubble levels that clamps on to the dovetail, so the gun and stock should be vertical.
I've seen others do it by eye, and the person I shoot with regularly does it empirically, shooting long and short until crossover goes away. Is there any other way?
It's plumb from the latin 'plumbum' meaning lead, for the weight on the end of the string.