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Optimal scope setup

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bandg:
Yes the 45 degree angle is extreme to make a point.  And your scenario is stated as a hypothetical as well.  But I don't see how you can argue the physical situation I laid out.  It doesn't matter that the 45 degrees is extreme and no one would shoot that way.  It does matter that it illustrates that different mounting heights will have a different point of impact with the same amount of cant.  Assume 6 degrees of cant which would still seem to be an amount most could see.  There would still be a difference, even if small, due to mounting height.  And I still don't agree with your view on the mil dots.  Yes they would be roughly aligned with each other but not similarly with the bore.  They would both converge on the bore and would have to do so at different rates.  I'll still believe that mounting height will have an effect on cant error.  That difference will be much more for longer ranges but is there at any distance other than the zero distance.  But the cant itself is the thing to focus on. 

nervoustrigger:

--- Quote from: bandg on November 27, 2018, 03:28:25 PM ---I don't see how you can argue the physical situation I laid out.  It doesn't matter that the 45 degrees is extreme and no one would shoot that way.  It does matter that it illustrates that different mounting heights will have a different point of impact with the same amount of cant. 
--- End quote ---

The physical situation you laid out is correct insofar as a higher scope will swing further from the 12 o'clock position, but the resulting cant error is only greater if the scope is also misaligned to the bore.  It's simply a different source of error.  Important, yes, but different and distinctly unrelated to how much the gun is being canted. 


--- Quote from: bandg on November 27, 2018, 03:28:25 PM ---I still don't agree with your view on the mil dots.  Yes they would be roughly aligned with each other but not similarly with the bore.  They would both converge on the bore and would have to do so at different rates.  I'll still believe that mounting height will have an effect on cant error.
--- End quote ---

Trust me, I know this is hard to sort out.  You are falling prey to the same geometric fallacies I was.

You agree that the mildots are roughly aligned to each other.  I will disagree with the roughly part...by way of the hypotenuse qualification I made earlier, there is indeed some difference in how precisely the two sets of mildots lie on top of each other but unless we separate the scopes vertically by a completely unusable amount, that difference is completely academic.

So ask yourself this, what is cant error if not "I was aiming here, but I had the rifle tilted so it actually hit there?  So if the mildot in each scope was on top of the point here when you pulled the trigger, the errors are the same and there is no difference between the two scopes.

bandg:
As simple as I originally noted-consider the two different height mounts "correctly mounted" and zeroed at ANY distance.  Then consider the rifle tilted at some angle (45 degrees for easy visualization but ANY angle).  Cross hairs stay on aim point and muzzle shifts out to the side.  Shots will hit at the same point at only one place, the zero distance.  They will hit at different points from the muzzle to the zero distance with the difference decreasing as they approach the zero distance when they will both hit point of aim.  Beyond that set zero distance they will again hit AT DIFFERENT POINTS with the difference increasing as long as the range increases.  If you can think of any way for anyone to verify what you claim then describe it.  Anyone can go to their back yard, "correctly" mount a scope with low mounts and then with high mounts, fire shots at a consistent amount of cant, and OBSERVE the change for themselves. 

Think of it more simply if it helps you understand-do the two different mounting heights hit at the same point from muzzle to zero and beyond even if "correctly mounted" and held perfectly level?  No, they do not.  They only hit at the same point at the zero distance.  The taller mount will hit more below the line of sight at/near the muzzle.  Surely you've heard discussions of holdover needing to be greater at very close ranges to hit a target with tall mounts in relation to low mounts.  It's the same thing.  Cant the rifle (remember you cannot cant a mounted rifle/scope setup independently as they are mounted rigidly together and "incorrectly mounted" has nothing to do with this) and the point of impact moves to the side along the same angle but the taller mount moves that POI slightly more to the side (it is a longer radius from bore to scope).  It is not the same.

nervoustrigger:

--- Quote from: bandg on November 27, 2018, 04:27:41 PM ---Anyone can go to their back yard, "correctly" mount a scope with low mounts and then with high mounts, fire shots at a consistent amount of cant, and OBSERVE the change for themselves.
--- End quote ---

Not so, and that statement runs counter to the well documented article that Scott posted at the beginning of the thread.


--- Quote from: bandg on November 27, 2018, 04:27:41 PM ---Think of it more simply if it helps you understand-do the two different mounting heights hit at the same point from muzzle to zero and beyond even if "correctly mounted" and held perfectly level?  No, they do not. 
--- End quote ---

No, but again that is unrelated to cant.  The difference you are referring to is one that affects elevation.  Cant is predominantly an error of windage.

bandg:
"No, but again that is unrelated to cant".  Nonsense.  It is directly related to cant since the scope is rigidly mounted to the rifle.  The radius is shorter for lower mounts than for taller mounts.  Simply draw it out to see. 

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