The rail should be part of the measurement only the top of it/bottom of the ring up is equated. An average od increase of 8-10mm beyond objective size on the optics I have seem to be norm. 50 objective is close to 60. Yup, didn't count for that. 1.200-1.250" for rings depending on manufacturer.But a 50mm objective is not a 50mm measurement on the outside of the objective bell.
Don't forget to add the Pic rail height to the equasion.
Here is a Kelbly Nanook SA, Proof Sendero contour, w. ARC 30mm low .94" rings and a NF NX8 2.5-20x50 for reference. Still clears the scope caps.
View attachment 497115
View attachment 497116