RE: sighting in a 270 H&R Single shot
I would sight in about 100yrds 1" high.
Shoot at 25 and 50 and 75 and 150 and 200.
Note where you hit and remember. If you change scopes or ammunition repeat process every time.
Shoot, shoot, shoot, and make each shot a learning experience.
You will find there is very little difference in POI, but the confidence of seeing it is priceless.