my range ( a sendero right behind a buddys ranch house) is being renovated so went from 100 yds to 78 yds temporarily. i need to sight in sons mod 70 30-06 that is usually sited in 1" high at 100 yds. what diff. will POI be at 78 VS 100 yds using 180 gr sierra RN over 46.0 varget? THANKS