Was it off at 1260? Im assuming the 4.2 Moa was the dope for 520? Have you checked your scope to see if the click values are true 1/4moa? I had a Nightforce and a USO both be a little off from their stated 1/4 moa adjustments. What do you think the reason for your 1/2 moa error was at 520? Do you think it was the rangefinder itself?
I have played with g7 ballistics calculator on the Gunwerks website and it was right on with my shooter app. The only time i noticed a difference was when i had the Shooter app setup for a scope that wasn't true moa.
