I know my brother and me shots to different zeros in several rifles we have sighted in, he can group them but they are of.
this is me being a LH and he being a RH to so the twist of the barrel factors in?
I think its caused by the way the rifle recoils when shot by lefties and righties. Rifles tend to move to the right before the bullet leaves the barrel when shot by right handed people; to the left for left handed ones. So, if the rifle's sighted in by a right handed person, a left handed one will need to make a windage correction to the left on the sights.