Thread: Change of zero at different altitudes?

I had a play with the Strelok app and it does exactly what you are trying to do!
You can set the altitude, temp and pressure for when you zeroed the rifle, and do the same for where you are shooting now. It doesn't try to keep you zeroed like the program you are using.
For my 243 load using your altitudes and temps, it predicts 0.3cm low at 200m (yes that's 3mm low, 0.05 MOA, so not much change at all.)
308 firing 178gr eld-x it predicts 0.7cm low at 200m, still only half of a quarter MOA click.