Here are my details:

Nosler 180 gr Accubond, 73 gr of IMR4831 powder, Norma brass (trimmed, weighed/sorted, neck turned, flash hole reamed, primer pocket uniformed, annealed every 3 firings), WLRM primer, 26" Hart #5 barrel, muzzle velocity of 3050 fps, altitude 1000 feet, temp 50 degrees, Magnetospeed V2 chronograph.

Magnetospeed said that if the chrono was bad, it would be very inconsistent. I'm getting ES of 28 and std dev of 9, so the velocity should be close. They said readings should be within .5%.

The calculator says I should be using 22 power. Even if I lower the muzzle vel down to 3035 (.5% reduction) AND lower the BC down to .482, I still get a power of 21 with the calculator. I have to lower the power down to 20 to get the correct elevation for 300 yards and the first hash mark.

Has anyone else successfully used the Zeiss ballistic calculator with the Rapid Z reticle?

Anyone have any ideas why the calculator isn't very close to real world?