I use that blue, clay-like, "dummy" glue to set my scope onto my rifle, then measure the thickness.
If only manufacturers would list some useful specs on their sites. The best I've seen for this is Sako/Optilock.
I have a Tasco Titan (30mm tube) 3-12x50 on a Savage 110 with a sporter contour and it JUST clears the barrel with Warne low bases. I actually had to file a flat spot on the scope cover to get it to fit between the bell and the barrel.
The height from receiver to the bottom of the scope is .525, half of which is the base, the other the rings. The outside diameter of the bell is 2.36".
Good luck.