Optimal scope setup



Author Topic: Optimal scope setup  (Read 1237 times))

Offline rsterne

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Re: Optimal scope setup
« Reply #20 on: November 27, 2018, 11:03:37 PM »
bandg…. I suggest you go back and read the article linked in the OP.... Pay attention to Chapter 3 "When a High Scope is Worse", and Chapter 4 "When a High Scope is Better".... My statement exactly agrees with those two chapters.... Go to ChairGun and input the data, and you will see for yourself....

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.... The article you linked says that any cant past 5 deg. is likely to be noticed and corrected by the shooter, and I would agree with that.... This means that the vertical cant error is very small, and the difference between a high and low scope even smaller.... In fact, at 5 deg. of cant, the vertical cant error is less than 0.4% of the total drop below the boreline, because (1-cos5) = 0.0038.... That is NOT the case with the horizontal cant error, which is what we are really concerned with....

I think your confusion about the vertical cant error is because the vertical POI is already different with a high scope.... You are correct that at 10 yards the impact with the 11.5" high scope will be well low, compared to the 1.5" scope.... but that is already the case, even with no cant.... The VERTICAL CANT ERROR does not change with scope height.... but the HORIZONTAL one certainly does....

Bob

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Offline Scotchmo

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Re: Optimal scope setup
« Reply #21 on: November 27, 2018, 11:24:15 PM »
...
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....

When POA matches the intended POI, than scope height NEVER matters with regards to gun cant. Not even a slight difference.

What do you mean by "AT the range you are zeroed"?
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Offline rsterne

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Re: Optimal scope setup
« Reply #22 on: November 28, 2018, 01:21:12 AM »
"AT the range you are zeroed" means exactly what you said.... POA matches POI when your target distance IS the same as your zero distance, so scope height doesn't matter....  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.... just as it makes a difference to the POI distance above or below the LOS/POA....

We are agreeing with each other, Scott....

Bob
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Offline Scotchmo

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Re: Optimal scope setup
« Reply #23 on: November 28, 2018, 02:18:53 AM »
"....  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...."


Ok. Agreed. Ranging errors will add another variable .

If the distance is different than our zero, than what we actually have is a range finding error, which results in a holdover error, which varies with scope height. If it is also canted, those errors are canted.

If all we have is gun cant error (no range finding error), scope height does not affect it. Hopefully, we all agree on that.
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Offline bandg

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Re: Optimal scope setup
« Reply #24 on: November 28, 2018, 11:55:27 AM »
If I recall correctly, in that same article (possibly it was another article related to "vertical cant error" search but I don't think so), the writer stated that he noted horizontal errors as expected but was surprised that the vertical error was much higher than he thought it would be in relation to cant.  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 but maybe I should put more weight on the vertical part as well.

I think in general we are all in agreement but not sure.  I use holdover but also use mechanical levels so I should not have to consider the effect of cant vs. holdover.  The levels eliminate the cant and any holdover I use should therefore be in the vertical plane. 

I also had trouble with this statement in reply #13-"a higher scope has less horizontal cant error closer than the sighted difference".  That is just wrong.  I'll simply go back to the basic mechanics.  Forget ranging for a second.  Consider rsternes 1.5"  vs 11.5" inch mounting heights in his original post.  Now cant the rifle the same amount for each height around the scope centerline as anyone would do firing a shot at zero distance.  Crosshairs on target but muzzle laterally moved to the side.  Classic cant error-aiming where you want to hit but rifle canted.  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.

This amount of closer than zero distance horizontal error would be small for either height.  But it is physically there and would be greater for a higher mounted scope than for a lower mounted scope.  It would probably be notable only in a situation where someone was zeroed at maybe 30 yards and shooting at a target at 10 yards.  You would have to hold over to hit the closer target (as normal) but 5 degrees of cant would move the POI laterally a small amount as well.  Enough to cause a miss?  Probably not but it depends on how small the target is and how high the scope is mounted. 

As Scott said before, mount scope correctly (level to bore) and hold it level when you shoot.  And the hold it level part seems especially important if you use holdover.

« Last Edit: November 28, 2018, 12:01:50 PM by bandg »
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Offline nervoustrigger

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Re: Optimal scope setup
« Reply #25 on: November 28, 2018, 12:35:20 PM »
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...

I agree, and it's pretty easy to see that in Perry Babin's animation here http://www.arld1.com/impactpointvscantangle.html
Swing the rifle just a few degrees and you can see the POI shifts much more to the side than it does vertically.  As you continue to increase the cant to unrealistic levels, the vertical becomes much more pronounced but for more realistic levels of cant, the vertical component is pretty much negligible.  Given the myriad of other factors like the basic accuracy of the rifle, the human element, and the wind, the difference would be pretty hard to discern.

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.

Consider the extreme scenario the target paper is right up against the muzzle of the rifle, and then let's put the two scopes above the bore and cant the rifle 45 degrees.  The high scope has a larger radius from the bore, thus it swings out laterally further than the low scope.  Thus if I compare where each of the reticles point on the target paper, the high scope is "more wrong".  But here's the problem with that...it's only because it is physically impossible to zero the high scope to the point of impact (nor the low scope, for that matter).  The erector tubes cannot angle downward far enough.  If they could, their errors would be the same.  Out at some more reasonable distance, that condition becomes possible and both the high and low scopes have the same error.
« Last Edit: November 28, 2018, 01:10:24 PM by nervoustrigger »
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Offline rsterne

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Re: Optimal scope setup
« Reply #26 on: November 28, 2018, 02:42:17 PM »
bandg, all I can say is that if I am incorrect, I am in good company, as my statement agrees with that linked in the thread in the OP.... I have copied the text below, you will have to follow the link to see the corresponding diagrams, should you choose to bother....

Quote
CHAPTER 4. – When a higher scope is better

And 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.

The key is not the height of the scope, but the distance between the LOS and the boreline at the distance you are shooting, the "canting error circle" described above.... With a high mounted scope that distance is less when you are shooting closer than the range the rifle is sighted at, than it is with a low mounted scope.... I see little point in continuing to argue with you, all you seem to be interested in is saying "That is just wrong"....

Have a nice day....

Bob
« Last Edit: November 28, 2018, 02:49:45 PM by rsterne »
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Online mobilehomer

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Re: Optimal scope setup
« Reply #27 on: November 28, 2018, 04:34:50 PM »
Mount two scopes, one above the other, if they are canted in the opposite direction there is NO WAY the reticles will align!!!
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Offline nervoustrigger

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Re: Optimal scope setup
« Reply #28 on: November 28, 2018, 04:47:49 PM »
Ken, that's true for most any meaningful amount of cant.  Typically there's around 60-90 MoA of adjustment in the turrets, meaning the erector tube can move +0.5° - 0.75° so that wouldn't be of much use to correct for any significant divergence of the two hypothetical scopes.

Offline Scotchmo

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Re: Optimal scope setup
« Reply #29 on: November 28, 2018, 05:11:49 PM »
Mount two scopes, one above the other, if they are canted in the opposite direction there is NO WAY the reticles will align!!!

If one scope is mounted directly above the other, with one scope rotated CW and the other rotated CCW, then you are describing scope-cant. That is a different problem and produces a subtly different error than gun-cant. Though many people confuse the two problems.

Scope-cant is a scope mounting issue. It is corrected by mounting the scope so that the vertical retical intersects the bore.

Gun-cant is a gun hold issue and is corrected by holding the scope upright when taking the shot.
« Last Edit: November 28, 2018, 05:14:07 PM by Scotchmo »
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Offline bandg

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Re: Optimal scope setup
« Reply #30 on: November 28, 2018, 05:15:05 PM »
Bob-

You're still just wrong.  But as you say, have a nice day.
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Offline Scotchmo

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Re: Optimal scope setup
« Reply #31 on: November 28, 2018, 05:17:29 PM »
If POA matches POI, and your gun/scope are setup correctly, gun cant errors are NOT affected by scope height - period.

Now, if you have a range finding error, or your dope is bad, or your scope is mounted incorrectly, or your gun is not sighted-in correctly - cant errors will be affected by scope height. But that is not strictly a canting error. Only when you have verified that every other issue has been corrected, then you can look at cant errors. There is plenty of bad testing methodology that thinks gun cant is the only problem, when in realty, a combined error existed. From that combined error, they make general statements that are not really true.

The first link that the OP shows:
www.szottesfold.co.uk/2012/03/high-scope-and-canting-end-of-ancient.html

I can't really find fault with his methodology or results. It's a good source.

Bandg posted a different link later in this thread:
www.riflescopelevel.com/cant_errors.html

That article made some good points, but had numerous errors. Makes the whole suspect.

Just because information is presented in a professional looking manner, does not validate it.
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Offline bandg

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Re: Optimal scope setup
« Reply #32 on: November 28, 2018, 10:21:02 PM »
Jason-

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.  Consider rsternes statement in #13-"a higher scope has LESS horizontal cant error closer than the sighted difference".  Nonsense.  As you described it has more error, not less. 

Scott-

In the description above, the higher scope has more lateral error near the muzzle than the lower scope.  I certainly think that should be obvious.  It is a small amount but it is present.  The DIFFERENCE in horizontal error between low and high mounted scopes DECREASES as the pellet moves toward the zero point.  They match at/near the zero point (ie both will hit the aim point).  But what has this done?  It has established an angle between the two lines of flight shot from the canted position in the horizontal plane.  Obviously the angles exist in the vertical plane due to convergence of bore to LOS (the scope) but forget that for a second.  Canting the rifle in the way described above establishes an angle in the horizontal plane.  The lower scope pellet starts out slightly closer to the vertical line than does the higher scope pellet.  But they both CONVERGE (both horizontally and vertically) as they move to the aim point where both impact at the zero distance.  BUT WHAT HAPPENS PAST THAT POINT?  DOES THAT ANGLE DISAPPEAR?  No, it does not.  The pellet will drop due to the force of gravity and slow due to resistance but ignoring wind (and other basically negligible factors like spin drift) it will continue along it's original VERTICAL line of flight.  But in the case of the higher mounted scope that is a larger angle than the lower mounted scope pellet was moving on.  So the pellet from the higher mounted scope continues to now DIVERGE from the lower mounted scope line as it moves beyond the zero distance.   Greater cant error from higher mounted scope than lower with that error increasing with distance.

Assume 25 yard zero.  The greatest DIFFERENCE between high and low mounts for any degree of cant will be at the muzzle, lessening to the common impact point at zero distance, then increasing to the exact same amount that was present at the muzzle again at 50 yards distance.  Simple geometry.  Not a lot of error for air gun distances.  But beyond that zero point distance the vertical line of flight of the two pellets will PROGRESSIVELY DIVERGE until they stop moving.  Both move away from the LOS (the vertical plane) beyond the zero distance but the greater angle for the higher mounted scope means it moves away gradually faster.  Greater error for higher mounted scope. 

If anyone wants to visually verify this, you would need a correctly mounted scope on your rifle.  If you have high mounts you would need to get low mounts and vice versa to compare the angles created but shooting what you have can easily illustrate the angle.  For more obvious results I would suggest more cant.  The best target to make is a simple sheet with a vertical line and a dot for aim point near the top of the line. Aim dot should be nearer the top of the sheet to keep drop on paper at longer distances.  You can use a protractor to put a point at a specific angle from the vertical to make cant consistent-crosshairs always on aim dot and lower vertical hair on the mark you make for consistent cant.  Put a target near the muzzle, cant and shoot.  Put a target at zero distance, cant and shoot.  Put a target at twice your zero distance, cant and shoot.  Same cant amount each time is important.  In each case you are putting the crosshairs on the target dot.  You are not trying to correct your aim to hit the dot but simply aligning the LOS (scope crosshairs) on the dot the same each time.  You will see the horizontal angle mentioned above visibly on the targets as the pellets make their holes (with a clockwise tilt it will be groups low/left near muzzle, groups near point of aim at zero distance, and groups low/right further beyond.  You will also see vertical movement (bore rise to zero distance and drop beyond) but that is present in all cases and can be ignored for this process.  Simply measure the distance from the vertical line through the aiming dot laterally (90 degrees) to the group impact point.  Must have little to no wind for this to work.  Then to see the difference related to height, mount the scope correctly with the other mounts and repeat the sequence. 

Make a little assumption here-25 yard zero and assume you tilt the gun enough clockwise to move the pellet impact point 1" left of vertical near the muzzle (remember, crosshairs always on the aim dot and always the same amount of tilt).  That impact point will be low and left of the aim dot near the muzzle.  At the zero distance the pellets will hit (impact point) very near the aiming dot.  Beyond the zero distance at 50 yards the pellets will impact lower (depending on gun/pellet velocity) but they will again be 1" right of the vertical line (same as at the muzzle).  There's that pesky angle again.  If you get larger paper for targets and continue to move the target away you will see the pellet falling dramatically lower due to gravity but it will continue to move laterally at a predictable rate due to the angle and distance.  Again, any wind will make it very difficult to get consistent results.

I really hate to argue with people about this.  But I have done exactly the above.  On calm days.  In the backyard with air rifles and at my 600 yard range with firearms.  I've looked at the targets with the holes in them.  I've seen a visible amount of cant move a bullet a couple of feet at 600 yards then immediately (no change in wind) cant the other way and watch them hit a couple of feet in the other direction.  If you want to illustrate this to yourself, give it a try.  You can go through this process with an air rifle and single mounted scope in an hour or so. 


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Offline nervoustrigger

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Re: Optimal scope setup
« Reply #33 on: November 28, 2018, 11:21:37 PM »
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.

That made me smile because I was thinking about writing something along similar lines when I replied earlier. :)  I noticed you prefer to make reference to "swinging the bore", and that's all well and good, and I prefer to make reference to "swinging the scope" because it's physically what I would do if I were sitting at the bench with the rifle resting in front of me.  I would leave the rifle where it is and tilt it to one side...that is, "swing the scope".  This preference really has nothing to do with an idea of aiming with the bore.

Whether we swing the bore or swing the scope makes no difference but it does seem to make it a bit harder to communicate our concepts to each other.

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. 

Okay, I'm carefully picturing the the scenario from your perspective....

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... 

Well, again I acknowledge the difference in the swing radius of the two scopes.  No question about that.  But the higher scope only has more error if it is not zeroed to the same POA as the lower scope..  For your contention to be true, it assumes the scopes' lines of sight (LOS) and the bore line are parallel.  But they aren't.  The scopes' erector tubes are angled so as to put the reticles onto a common POA...when both scopes are zeroed, their reticles literally superimpose on top of each other.  Whatever error one has by way of canting the rifle, the other has the exact same error.

The obviousness of the larger swing radius makes it very tempting to think the high scope is worse.  In fact the author linked in the original post covers this common misconception very early in the article:

Quote
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...

Offline Scotchmo

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Re: Optimal scope setup
« Reply #34 on: November 29, 2018, 12:29:39 AM »
...Assume 25 yard zero.  The greatest DIFFERENCE between high and low mounts for any degree of cant will be at the muzzle...
Do you know the difference between scope-cant and gun-cant? Your statement is true for scope-cant. But if a gun has been setup correctly, scope-cant will not exist.

If you are canting a correctly setup gun, your statement that I quoted above is obviously wrong.

Gun-cant errors are a function of gravity acting on the trajectory at an angle away from vertical. At the muzzle, gravity has not yet affected the trajectory. If the trajectory is not affected, it should be obvious that there will be no gun-cant error.

I now think that you are confusing the calculations used for scope-cant with the calculations for gun-cant. That is a common occurrence when someone attempts to analyze and quantify cant errors.

Think about this:

1) Scope-cant errors can happen even in zero gravity.

2) Gun-cant errors DO NOT happen in zero gravity.

Now - which of those two are you talking about?

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Offline bandg

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Re: Optimal scope setup
« Reply #35 on: November 29, 2018, 12:54:18 AM »
I don't agree, and I'm not assuming parallelism.  Parallelism would mean you would never hit the target, you would always hit low.  Bore has to converge with scope/LOS.  And if you "swing the scope" then you aren't aiming any longer.  When shooting, you are looking through the scope and aiming at the target.  Cant arises by unintentionally tilting the rifle but a shooter would still be putting the crosshairs on the POA.  How else do you aim?  The crosshair is the only aim point you have.  You can talk about swinging it in theoretical terms and therein arises the confusion.  How in the world could you "swing the scope" and still be able to aim" 

I am assuming the same zero distance for both high and low scope and the same POA.  Assume no cant, scope mounted directly over bore, rifle held level.  Everything perfect.  Assume a low mounted scope has bore 1" below scope.  High mounted scope has bore 2" below scope.  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).  This must be true for both to hit at the same point at the same zero distance.  Now below that horizontal line (representing both scopes/LOS) draw a first line representing the low mount situation with bore starting 1" below the scope tilting up to the POA and a second line below that representing the high mount situation with bore 2" below the scope (1" below the low mount) again angled upwards toward the POA.  Both scopes are level and aimed at the same point (represented by the main horizontal line).  The low mount situation starts the bore closer to the scope and it tilts less steeply upwards as it moves to the POA.  The high mount situation starts the bore further below the scope but it tilts more steeply upwards to the identical POA.  2 theoretically superimposed scopes with the different mount heights resulting in different bore tilts.  Draw it out.  That lower line being below the middle line is the difference in low and high mounts.  Both bores converge to the single common aim point but the higher mounted scope will have the shot below the lower mounted scope out to zero distance where they meet.

Now introduce the unwanted cant.  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.

If this doesn't make sense to you then we are discussing the concept using profoundly different views of mechanics.  I'm not capable of viewing it any other way because it isn't logical to me.  How do you hit anything without having and keeping the scope aligned on the target?  "Swinging" the scope is not something I can practically get my mind around.  Obviously anything can be moved in space, tilted, up/down, left/right, whatever direction one wants to move it.  But to fire a shot and hit a target the aiming mechanism (the scope in this case) must be aligned directly on the target.  Cannot understand "swinging" that.
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Offline bandg

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Re: Optimal scope setup
« Reply #36 on: November 29, 2018, 02:01:33 AM »
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 that start at two separate points but converge with each other to the zero distance aim point just as each converges with the LOS to that point.  They must converge so that each can impact at the zero distance aim point.  How can the greatest difference between the two paths be anywhere but at the muzzle if they are converging as they move away from the muzzle?
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Offline Scotchmo

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Re: Optimal scope setup
« Reply #37 on: November 29, 2018, 02:39:20 AM »
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...

Not true.

The projectile path from the muzzle to the bullseye is exactly the same regardless of scope height.

The scope has no affect on the pellet's trajectory.
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Offline nervoustrigger

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Re: Optimal scope setup
« Reply #38 on: November 29, 2018, 10:42:18 AM »
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.

Okay, I see your aversion to my approach.  You want to hold a particular unchanging point of aim, let's call it POA-A, and I can understand why you want to do that.  However my interest is exploring the point of aim versus the actual point of impact, and for that it does not matter.  In other words when I swing the scope to cant the rifle, I have a new point of aim, POA-B...but then when I fire, I realize my POI wasn't at POA-B.  That's all.

That line represents both scopes and as you note the reticles are superimposed.

This.  Focus on this part.  If both reticles are superimposed on top of each other, and the reticles represent your point of aim, how can one have more error than the other?

Offline nervoustrigger

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Re: Optimal scope setup
« Reply #39 on: November 29, 2018, 10:47:20 AM »
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).

By the way, I think the bold part is where the logical error arises.  The bore does not tilt upward differently for one scope versus the other scope.  The bore is fixed, and instead each of the scopes is tilted differently.  They have to be in order for their points of aim to be identical.

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