With a 100 grain bullet sighted in to hit 1.5 inches high at 100 yards you will be back at zero somewhere close to 200 yards and at 300 yards about 7 inches below your aiming point.

Sighted 2 inches high at 100 yards will put you aproximately 4 inches low at 300 yards.

This is just a estemate. To know for sure do like driftrider said and go shoot at different distances.