...There is no difference in the cant error between a high and low scope AT the range you are zeroed, but there will be a slight difference at all other distances....
".... However, if you are sighted at a given distance, and shooting either closer or further away, the scope height can make a slight difference to the cant error...."
Personally, I've always thought of cant error only in terms of the horizontal movement since I considered it a greater effect on accuracy than the vertical component...
It is IMPOSSIBLE for the higher mount condition to not move the muzzle more laterally than the lower mount for any given amount of cant. Simple geometry (the longer radius) and mechanics (the scope is bolted rigidly to the rifle). Cant the rifle any amount and a higher mounted scope will cause the bore to shift more laterally than will a lower mounted scope. MORE horizontal cant error closer than zero distance, not LESS. The radius from scope bore (LOS, point of aim)to muzzle is longer for the higher mount thus the muzzle will move slightly more laterally caused only by the relative height of the scope mount in this situation. Thus a higher mount will cause slightly MORE cant error at any range closer than zero range than will a lower mount. Beyond zero range the error will also be greater for a higher mounted scope and will gradually increase due to continued divergence of flight path from vertical until the projectile stops. MORE error at longer ranges and progressively MORE error for higher mounts at longer ranges with any amount of cant.
CHAPTER 4. – When a higher scope is betterAnd now let's see the opposite instance. The rifle still has two theoretical scopes on it, a low and a high one. Both scopes are zeroed at range 'R0' but this time we shoot at distance 'R' which is SHORTER than 'R0'.The rifle which is zeroed at 'R0' doesn't hit at range 'R' because the bore looks above the target with 'L' (low scope) and with 'H' (high scope) instead of 'D'. The relation of the red, blue and green points can vary with ballistics but 'L' is always MORE than 'H'.So we aim with the crosshair at a point which is above or below the target with the appropriate amount 'LA' and 'HA'. In this case, when the bore line hits the target plane with 'L' and 'H' above the aiming point and in both cases with 'D' above the target, and when the pellet drops with 'D' then it hits the target.If we cant the rifle, the bore line is rotated around the LOS – but they are different with this aiming method. This means that the radius of the canting error circle is 'L' with the low scope and 'H' with the high scope and 'H' is smaller than 'L'. This means that in this case the higher scope gives LESS canting error.
Mount two scopes, one above the other, if they are canted in the opposite direction there is NO WAY the reticles will align!!!
Take the second paragraph in your post #25. It is accurate but I think you are trying to view it the hard way. You don't aim with the bore, you aim with the scope.
Take the exact premise that you described there but put the crosshairs on the target dot (your aim point at zero distance) and rotate the rifle (muzzle/bore) below it. That is the way cant works for an actual shot at zero range. Forget holding over or clicking to change zero. That does change everything.
Put the crosshairs on aim point at zero distance. Just like you would do to shoot at a target at zero distance. It is basically the same as you described but seems much easier for people to imagine. If you do that you will note, as you mentioned, that the higher mounted scope has more error (it causes the muzzle to move further to the side than does the lower mounted scope) exactly due to the radius...
CHAPTER 1. – Misbeliefs...An old gunsmith explained it to me in the following way, this is the simplest mistake which says that the higher scope means more offset when canted with the same angle:Of course this is right only if we shoot at a paper which is immediately in front of the muzzle. The bore line and LOS are not parallel, and the LOS' of different scope heights intersect on the target so the displacement is the same...
...Assume 25 yard zero. The greatest DIFFERENCE between high and low mounts for any degree of cant will be at the muzzle...
Scott-PM sent. I do know the difference. The quote you say is not right for a correctly set up scope/rifle is simple geometry. With a correctly set up scope and rifle and a common zero distance, two different scope heights will produce two different projectile paths...
In actually firing a shot, how could you "swing" the scope anywhere. The scope is your only defined aim point and to hit a target it must be and remain aligned on the target. The cant error results from no longer having the rifle (the bore) directly below the scope. The scope is still aimed at your target (why would you "swing" it off target?) but the bore has moved laterally below the scope.
That line represents both scopes and as you note the reticles are superimposed.
Both are SCOPES are aimed at the same POA and at the same distance. You can represent this easily with a horizontal line representing the scope/LOS from front of scope to a target. That line represents both scopes and as you note the reticles are superimposed. But the bore tilts upwards less for the low mounted scope (bore starts closer to scope/LOS) and tilts upward more for the high mounted scope (it starts further from the scope/LOS).