I have a conundrum brewing.

I am using Shooter, Strelok Pro, JBM, and Hornady's calculator from its website.

Using the *exact* same input data, all four calculators are giving me different output, and some of it is off by as much as a full mil at distance (700y)

Based on real-world testing, Strelok appears to be the closest so far, but I have a lot more testing to do.

I'm confused. While I accept that each program may use slightly different formulas, or apply atmospherics slightly differently, or flat out contain errors, I'm shocked that all four well-known calculators would be so far out of agreement. This is especially troublesome given the magnitude of popularity of these programs over the last ten years or so -- I assume each one would be fully mature and tested by now, given various user reviews of each.

Does anyone have any comment?

Thanks.