Measure your turret diameter
Calipers across the elevation turret is the easy way. No calipers? Wrap a thin strip of paper around the turret, mark the overlap, measure that length with a ruler, and divide by 3.1416. That's your diameter. We use it to print the tape at your turret's exact circumference, so it wraps edge to edge with no trimming.
wrap length ÷ 3.1416 = turret diameter