Any time that you're using more than one measuring device - of any type, for anything - both will need to be calibrated together to ensure that they actually read the same. Otherwise there will be an error.
For example, in this scenario, if you use two Chronys and one reads just 2% high and the other 2% low - which would be pretty good manufacturing consistency - you have a potential difference of 4% in the FPS readings for the same shot. That difference could be significant when calculating Ballistic Coefficients, particularly if the variability between the two units is more than that.
But if the two units are calibrated - ie their reading of a known single shot under identical conditions is known - then, yes any two chronys could be used as suggested. Mind you, I would be quite likely to hit the one downrange near the target. That wouldn't be good
For example, in this scenario, if you use two Chronys and one reads just 2% high and the other 2% low - which would be pretty good manufacturing consistency - you have a potential difference of 4% in the FPS readings for the same shot. That difference could be significant when calculating Ballistic Coefficients, particularly if the variability between the two units is more than that.
But if the two units are calibrated - ie their reading of a known single shot under identical conditions is known - then, yes any two chronys could be used as suggested. Mind you, I would be quite likely to hit the one downrange near the target. That wouldn't be good



