Legionnaire, Your one of the few people I've meet who understand the purpose of A/O. They're not really for shooting stuff a extreme long range..... they're for shooting teeny tiny groups extreme short range. That's why air rifle scopes are almost always A/O. The optical illusion we call "parallax" is most pronounced at short range. Look at the increment markings on an A/O scope. 3/4ths of the scale is from 10 yds to 100 yds. The adjustment from 400 to 500 yds is a tiny little sliver.
By liability I mean A/O adds cost, weight, complexity, frailty, and size. In return it helps you shoot one hole groups at 15 yds. Not a real advantage in a hunting rifle. How would one even use A/O on a hunting rifle? You gotta know the range exactly, not an easy feat once you step off a marked shooting range and start pursuing moving game on even ground. You see a coyote at 200 yds (assume you know 200 and not 247). You got 7 seconds to take a shot. Do you: A) Raise the rifle and shoot. B) Crank the power ring from 6x to 12x. C) Fiddle with the A/O bell and turn it from 150 yds to 200? My answer is "A", I've tried B & C and went home empty handed.
There's actually an easier way to minimize parallax - pick your rings and base so your eye lines up perfectly with your scope when you cheek is welded to the stock. I like using leather cheek pieces on my rifles. Parallax is the perceived movement of the cross hairs relative to the target caused when you move you're eye relative to the ocular lens. Here's the key point: If your eye is always in the exact same spot you will see no parallax at any range. This also gets back to the air rifle shooters since they have to dismount their single shot rifles every time they shoot.
Having said all this let me add that I personally do own a number of scopes with A/O. I'm not sure they help me shoot significantly smaller groups but they look cool and I like gizmos as much as the next guy, however when I'm hunting I'll set them on a fixed range and mentally duct tape them in place, same goes for the power setting on my variables. Life is short and I've missed to many opportunities messing with hardware instead of pulling the trigger. -- Kernel