I *LOVE* my Leupold Comp 40x!
I have a 4" wheel on it and range near-to-far fairly quickly, stop when it's sharpest. I note the yardage, then range again just to make sure I get the same number. If these 2 numbers are different, I'll do it a 3rd time (and pay a bit more attention this time). I use a close focus adapter for anything less than 11 yards.
This works for me, and I sometimes take along my laser rangefinder to record the distances after I'm done my lane (most of our matches are informal and everyone trusts one another) and the 40x is never more than 1 yard off, if at all.
It has taken me awhile to achieve this level of confidence though, compared to a Nikko 10-50, it's more difficult to use.
I've also tested the ranging at various temperatures, from about 8C to over 25C and haven't experienced any temperature shift - I'll never sell this Leupy - it's my
I sold my 35x because the depth of field was too long & I couldn't "learn it". I still have my 45x (which really 'snaps' into focus when compared to the 40x) but I just don't 'trust it' like my 40x - I haven't done as much testing with it, but I think it's a bit temperature sensitive.