Well, I've learnt something here, guys. Ruger 243's variable is not branded 'Champion' but the dot in the circle on the turret suggests it does have a constantly centred reticle. Does tunnel vision increase as the power is turned down? If not, I would be inclined to think they may have gone back to the Kollmorgen/Weaver method of doing it. Trouble with that would be that the reticle may not be as easy to change over, as it would then need to be part of the erector tube. On the other hand, that little dot-circle symbol may be on the turret in case of change-overs, indicating the system is the same as with the fixed powers. How it could work then puzzles me, though, because the reticles in the fixed powers were always specific to the magnification, which would be printed on the turret, too.
Yes, Klenchblaize, having the reticle go out of centre was the bane of the old scopes, which is why for many years I would have them mounted by a competent gunsmith who would mill bases etc to see things lined up. At home I use adjustable mounts for windage and shims to fix elevation.
That all sounds like a PITA but is justified for the reasons I mentioned earlier. There is, however, a new school of thought that says even image-movement scopes should be mounted straight for optical and mechanical reasons and that great care should be taken not to bend the damned things. If they are right, then what is the point of constantly centred reticles in low-powered scopes?
Certainly an out-of-centre reticle quickly becomes apparent in high-powered scopes, but I find in scopes up to about 4x you can be two or three inches off centre at 100 yards without noticing it - and this is the same margin of error that gurus like William Hambly-Clark Jr allow in their modern, image-movement scopes.
He uses the roll-over technique to ensure his scopes' reticles are centred (set the tube in V blocks and adjust the knobs until the reticle stays on a target when rolled around through 360 degrees). My gunsmith mate uses that method even with my reticle movement scopes - I just eyeball them, so in this context, find they are quicker to adjust than the new ones
The tendency of scopes to bend, I think, comes from the move from steel to alloy tubes while sticking with the one-inch tube size. The old European scopes used to be 26mm when steel but something fatter in the dural version. The latter usually had rails, too, not only for mounting but to stiffen the tube. The old, dural Zeiss/Hensoldt and Nickel 1.5-6x variables had 30mm tubes 50 years ago, decades before extensive adjustments for long shots became the rage.
The easiest answer I can think of to all these problems is Burris Signature scope rings, which have Nylon-type inserts that swivel like ball joints until you tighten the screws. In the event the scope does not line up, you can get eccentric inserts that work in all directions. They even prevent the scope from getting scratched.