Being a long time iron sight shooter, who uses scopes in much the same way, I use the following approach to sight-in distances for hunting:
First, I determine the size of the target's kill zone. For example, I choose 3/4" for a squirrel.
Second, we all should know about the technical definition of "point blank range". It is, the maximum distance where the projectile does not go over the height of the kill zone and does not fall below it when using a center hold. I choose a bit different concept. My hold is at the bottom edge of the kill zone: a six-o-clock hold with irons or with the scope cross-hairs. Then, using Chairgun or other ballistics programs, I find the distance where the projectile's maximum height is the kill zone diameter above the line of sight. This actually increases the effective point blank range from that of a center hold. Note: the correct height of the sights over the bore is very important for the ballistics programs to work accurately.
Third, I sight in at this distance and verify with another target at the maximum height range that that the point of impact is not above my kill zone. I learn what these distances look like in the field. With targets at the maximum height range, I'll shade my hold down just a tad, while those at the maximum, I generally consider getting closer if practical. Otherwise, if I'm confident I'll hold closer to center.
Paper targets at known ranges get a different treatment to sight-in, of course. And, for the game of field target I use 1/2 mil-dot holds. However, with the Hawke 10x fixed power scope I use for this game, the trajectory height is right at 30 meters and intersects the 1/2 mil-dot above the cross-hairs. This is my sight-in range and hold for field target.
