Ian M,
OK I see what your driving at. I'm not an optics engineer and won't even come close to try to explain the design of scopes and optics, but here's my limited understanding.
Notice in your (2) 1/8 click models you mentioned that they are much higher power than your 1/4 click models. Due to limitation of optics with focus distances, restricted size of a rifle scope and such, if you go up on magnification you loose some things. And one of them is adjustment range. This is independent of the click value though. If you look over any of the scope manufacturers reference charts you'll notice the higher the magnification the lower the total adjsutment range as a general rule. This included 1/4 or 1/8 click value. As you mentioned before different scope models and manufacturer due vary a little.
A prime example to show the difference in magnification vs adjsutment range is the (2) Nightforce Benchrest models the 8-32 and 12-42 models both with 1/8MOA clicks almost exact same size lenses and outside dimensions. The 8-32 model has 50in of travel for elevation and windage. But the 12-42 only has 40in in both directions. Same sized 30MM tube, same diameter lenses, etc, etc. I beleive this is the difference your seeing in the amount of travel of 1/8 vs 1/4 click scopes. Almost all scope with 1/8 clicks are in the higher magnification range so it would be easy to come to that conclusion.
Hope this explains it somewhat clear than mud. Or another way to look at it is if I take an existing Leopold scope that has x amount of travel and send it to Dick Thomas of Premier Reticles to change the click value to something finer, I'll get back a scope with the same amount of travel still in it, but the click value will change to a finer or courser value depending on what work is done because all else stayed the same within reason.
Everyone have a great Independence Day!
Steve
