CANT , and it's effect ?

[nervoustrig]

If the scope has been installed canted, the cant error is affected by scope height.

If the scope is installed correctly and the gun is being held canted, the cant error is not affected by scope height. 

There's a good in depth discussion on the topic here:
https://www.airgunnation.com/topic/buble-level-anti-cant-device/page/2/#post-172251

And a demonstration using two scopes, one mounted 58mm high and the other 110mm high (almost twice the height). Shooting through each scope at different cant angles produces groups that lie on top of each other. 
http://www.szottesfold.co.uk/2012/03/high-scope-and-canting-end-of-ancient.html

 

[bandg]

If the scope has been installed canted, the cant error is affected by scope height.

If the scope is installed correctly and the gun is being held canted, the cant error is not affected by scope height. 

There's a good in depth discussion on the topic here:
https://www.airgunnation.com/topic/buble-level-anti-cant-device/page/2/#post-172251

And a demonstration using two scopes, one mounted 58mm high and the other 110mm high (almost twice the height). Shooting through each scope at different cant angles produces groups that lie on top of each other. 
http://www.szottesfold.co.uk/2012/03/high-scope-and-canting-end-of-ancient.html

Incorrect. Was then and still is. What I posted shows this, even though it isn't as precise as I'd like it to be. Open sights (low) produce less cant error. Scope (high) produce more cant error. Pretty simple, as another poster here stated. I may try a better setup at some point but some people will never be convinced so I don't know that I'll waste my time. I understand how it works. Those who agreed with me here also understand. The people who wrote the linked articles and mention scope height as a factor affecting cant error understand.

 

[nervoustrig]

Like Scott has lamented at times, it is a myth that will probably never die. In fact, the circle analogy described by Micro is the reason I stubbornly held onto the wrong understanding for so long. 

 

[bandg]

Your "understanding" is wrong now. It is as I described. I showed that physically by actually shooting, not reading an article. Some people have trouble grasping WHY it happens but it happens. I read through the AGN post you linked and even "Scott" stated in that post that there may be "some cases" where higher mounts cause more cant errors. There can't be "some cases". It either happens or it doesn't. I showed physically that it did. I do hope you grasp the concept at some point.

 

[nervoustrig]

Thanks for the well wishes but I repeated the two scope experiment described by Andras and there was no difference.

 

[bandg]

Not sure who "Andras" is but pictures of those results would certainly be interesting.

 

[Micro]

It's a pendulum problem - if a pendulum of a fixed length, swings in a controlled arc, the end or tip of the pendulum covers a certain distance; now lengthen the pendulum, and the tip will increase the distance it covers - the only way the lengthened pendulum will cover the same distance is to reduce travel or in this case cant. I think it helps to remember that the arc or angle of cant remains the same, but not the distance; put another way, a 1/4" group at 25 yards is theoretically 1" at 100 yards - nothing has changed except for the distance.

 

[Gunnertrones]

Bandg

Yes scope height matters as it increases so will the effects of cant. If you believe that you too believe what others here call a myth. And you are right just like the military and science. Because its not a myth its a fact.

After reading your above post and this one, I'm confused about what you are saying. Please be painfully clear so all can understand. Does increasing scope height increase the amount of cant error. I say it does and many others call that a "myth". Unfortunately, I'm not clear on what you are calling a "myth". Gunnertrones agrees with those that say scope (or sight) height does not matter. I say it does. Feel free to clarify with a simple "yes height matters" or "no height doesn't matter".

Once again. Rifle cant matters. Scope HIGH do not, because the scope (or iron sights) do not effekt the flight of the pellet. I mean, we talk about the impact on the target - yes?
Example: you fasten the rifle in a bench canted left. The impact, will hit left low. You unscrew the scope and fire a round, now using the “iron sights”. The impact will be the same. 
I know this is oversimplifying, but do not know a better way to describe the fact. 
The shooters behaving (rifle hold) effected by the high/low mount is a different issue, but not what we are talking about here. 

 

[bandg]

Bandg

Yes scope height matters as it increases so will the effects of cant. If you believe that you too believe what others here call a myth. And you are right just like the military and science. Because its not a myth its a fact.

After reading your above post and this one, I'm confused about what you are saying. Please be painfully clear so all can understand. Does increasing scope height increase the amount of cant error. I say it does and many others call that a "myth". Unfortunately, I'm not clear on what you are calling a "myth". Gunnertrones agrees with those that say scope (or sight) height does not matter. I say it does. Feel free to clarify with a simple "yes height matters" or "no height doesn't matter".

Once again. Rifle cant matters. Scope HIGH do not, because the scope (or iron sights) do not effekt the flight of the pellet. I mean, we talk about the impact on the target - yes?
Example: you fasten the rifle in a bench canted left. The impact, will hit left low. You unscrew the scope and fire a round, now using the “iron sights”. The impact will be the same. 
I know this is oversimplifying, but do not know a better way to describe the fact. 
The shooters behaving (rifle hold) effected by the high/low mount is a different issue, but not what we are talking about here.

"the scope (or iron sights) do not effeCt the flight of the pellet". 

This is correct in terms of absolute gravity. The pellet will always follow an arc determined by gravity. But it is incorrect in the relative terms of shooting because the sights are always OFF THE BORE. Some low, some much higher. This creates differences (relative) in "flight of the pellet as can be seen with required zero distances and changes in MPBR with different sight heights. 

Consider this-zeroed at 20 yards with low open sights, the pellet would rise VERY LITTLE (if any) in relation to LOS at ranges beyond 20 yards and would very quickly fall below LOS. Any rise above LOS would be such a small amount that you would never "hit high". But with a high mounted scope, the same 20 yard zero will result in a RELATIVE pellet arc that goes well above LOS at intermediate ranges before that pellet returns to a second "zero point". The high mounted scope would absolutely "hit high" at intermediate distances by an amount DIRECTLY RELATED TO HEIGHT OVER BORE. I believe that this is where those who do not grasp the concept go astray. They try to think of the ballistic arc of a projectile in its ABSOLUTE terms (as determined by gravity only) and not in it's RELATIVE terms (which is obviously still primarily controlled by gravity but is impacted in a slightly different manner by gravity due to the ANGLE between LOS and bore). That same process carries over to and is directly related to the horizontal cant error. The height of the sight over the bore sets a fixed angle that converges the bore to line of sight at the zero distance. That same angle (the absolute factor) then DIVERGES INCREASINGLY further from LOS beyond that zero point. The problem arises when people cannot seem to grasp that the VERTICAL component of that divergence is LESSENED by gravity pulling the projectile back toward LOS (the gravity determined ballistic arc). However (and this seems to be the critcal and not often grasped part), when cant is introduced, the effect on the vertical component is still controlled primarily by gravity while the HORIZONTAL component is independent of gravity and is determined ONLY by the angle introduced by the cant. Obviously the pellet shot with that horizontal angle introduced by the cant will still drop as it moves horizontally because gravity is always there, but the amount of horizontal movement is not determined at all by gravity. The amount of horizontal movement is determined ONLY by the angle created by the amount of cant PLUS the height of the sight. And the amount of DROP will be determined almost entirely by gravity and only slightly influenced by the inclination/declination angle. But the amount of horizontal movement (the "cant error" that I am most concerned with) is not detemined by gravity at all. That horizontal component is determined ONLY BY THE ANGLE.

If a shooter CLICKS TO ZERO correctly for accurately known distances then the above is moot because ANY height sight would be aimed directly at the zero point. But this would be true ONLY for that single specific distance.

I'm tired now but I believe the above is valid and can be physically tested by shooters IF they want to take the time to do so.

 

[nervoustrig]

Your "understanding" is wrong now. It is as I described. I showed that physically by actually shooting, not reading an article. Some people have trouble grasping WHY it happens but it happens. I read through the AGN post you linked and even "Scott" stated in that post that there may be "some cases" where higher mounts cause more cant errors. There can't be "some cases". It either happens or it doesn't. I showed physically that it did. I do hope you grasp the concept at some point.

The question is whether a high scope is more susceptible to cant error than a low scope. To answer this question, which of these two experiments would best answer it?

1. An experiment with two scopes
2. An experiment with a scope and a "not a scope".

A scope allows one to re-zero for every shot, either by using using stadia markings (mildots) or by dialing. Open sights do not do that except in a crude, improvised way analogous to holding over with a plain crosshair reticle absent of any mildots.

 

[thomasair]

Jason (nervoustrig) is correct. I had to do a very lengthy simulation in CAD a long time ago to prove it to myself.

If actual testing did not show the same results...it’s because the testing methods were flawed.

This idea that this happens is right up there with the idea that you can drop pellets that are not round through a round hole to determine their diameter...and once you’ve done this you can then see what your barrel “likes”. It will never go away and there will always be poorly acquired data to support it.

Mike 

 

[Micro]

In my last example, I will attempt to explain some of the causes for confusion about this most important aspect of shooting. All testing will take place in a perfect environment - a vacuum with no gravity so all environmental variables will be considered. Two identical rifles with identical scopes are mounted; one at 1.5" above the bore, and the other three inches. Both rifles are sighted in at 50 yards, capable of near one hole groups, and are installed in mechanical rests which allow rotation of 360 degrees around the axis of the bore or z-axis. Just to be clear, the relationship of the bore and sight on the target are fixed and will not change through full rotation. It's no surprise that both guns consistently fire pellets into nearly the center of the target through various points of rotation - even when upside down! The conclusion is of course, rotation or cant does not have any effect on where the pellet strikes the target; but more importantly and for our purposes, the relationship between scope height and barrel is of absolutely no consequence. Before I continue I should mention that I didn't specify whether or not the guns were sighted in with the vertical and horizontal stadia of the crosshair in the scopes were perfectly plumb and level - according to our experiment it doesn't matter - right? In fact, and we're all obviously in agreement it's important to assemble facts to produce the desired result, I have created an environment to prove a condition - absolute proof, that doesn't exist. In the nutria video, we see what appears to be rotation or cant of the crosshair from the horizontal or what we perceive to be level - the question is what is rotating, the barrel or the scope? It doesn't matter - right? It should be clearer by now; but I would like to conclude by removing both rifles from their mechanical rests, out of the controlled test environment, sight in on the bullseye and fire them at 25 yard targets set up in my backyard while being held at 90 degrees from horizontal - which one would group closer to the center or has the likely hood taking game? No, the relationship between scope height and cant affecting accuracy are not a myth, old wives tale, something that nasa and the militaty don't understand or any other statement - that's a fact. Further understand of this subject and point blank range can be done by reading, "The Book of The Rifle", by Jim Carmichael; this definitive work by one of the greatest shooting sports writers of all time, competitive shooter, hunter, mechanical engineer, gunsmith, trusted advisor to some of the worlds largest gun manufacturers, etc. touches on many aspects shooting and the conclusion he draws is to mount the scope as close to the bore as comfortable.

 

[bandg]

Jason (nervoustrig) is correct. I had to do a very lengthy simulation in CAD a long time ago to prove it to myself.

If actual testing did not show the same results...it’s because the testing methods were flawed.

This idea that this happens is right up there with the idea that you can drop pellets that are not round through a round hole to determine their diameter...and once you’ve done this you can then see what your barrel “likes”. It will never go away and there will always be poorly acquired data to support it.

Mike

You (and NT) are wrong. Micro is correct, as are others who believe the "myth". The really good thing about this issue, though not easy to do but possible, is that every shooter COULD verify it for themselves. I was in the process of that long winded post above while you were writing this. I stand by that post and do not agree with you, NT, or others who hold that same view.

 

[thomasair]

Jason is a good man for spending the time he does to educate people on the forums. It’s a big job to refute all the nonsense that’s continually spouted...but he fights the good fight. I commend him for that. I’m solely a competitive shooter and I actually prefer that my competition clings to all manners of ignorance concerning accuracy. It makes my life easier, if I’m being honest. Carry on fellas.

Mike

 

[Micro]

This reminds me of the recent PBR thread in which raising scope height, stating that adjustable objectives was preferable to side focus and duplex reticles accompanied by mathematical calculations to range a target were superior to advanced reticles with sub tensions. An apology was eventually made and it's possible that one may be forthcoming here, but I won't hold my breath. 

 

[nervoustrig]

It so happens the apology / concession you are looking for is contained in the AGN thread I linked earlier.

 

[fuznut]

No a high mount is no more susceptable to cant than a low mount. In fact it is less because it is easier to see the error.

Draw a plum line lock down the gun with plum line in the center of the bore. now imagine a t square mounted to gun centered to the plum line. Move the scope up and down the mount, the vertical lines will not move off plum line. Now cant the gun, move the scope low as possible. Look through it, then move scope as high as possible and look through it now. The high position will give you the impression it is canted more than the lower setting. Draw a line on target matching the horizontal line of scope at both settings move the scope back and forth from one setting to the other the horizontal lines of each position will be the same. But the higher position will be farther off the plum line so its poi will be effected more from the same amount of cant than the lower position. The poi of pellet will be the same ( very close) whether the gun is canted or not barrel straightness or lack of will cause slight diffrences . The prob with canting comes from our aiming . What part of that do we not agree on.??? Sorry but i cant tell lol.

 

[harrymoreland]

The question was in relation to the distance from the bore and the trigger, nothing to do with scope cant.

It has turned into a theoretical Mexican standoff. I am none the wiser. 

Good luck folks.

 

[Scotchmo]

... I read through the AGN post you linked and even "Scott" stated in that post that there may be "some cases" where higher mounts cause more cant errors. There can't be "some cases". It either happens or it doesn't. ...

That is true, and there are also "some cases" where higher scope mounts cause less "cant" errors.

When your POA does not match your intended POI, then errors resulting from cant will be affected by scope height. But is that really a cant error? I consider it an aiming error, the same as miss-ranging. True holdover (aiming above the intended POI) errors and ranging errors are both aiming errors, and both are affected by scope height. High scopes make both of them worse at closer range, and less at longer range.



If you are clicking-on or using vertical graduations on the reticle as holdover aim points, then scope height has no affect on gun cant errors. Gun cant errors are determined by cant angle and amount of projectile drop - and that's all.

Would the amount/effect of cant be decreased considerably by the trigger/grip/hand being, say, half the distance closer to the bore. 

Or am I way off on this thinking (as per most "thinking" I do"

No, though it could affect the error magnitude of a "pulled" shot.

 

[bandg]

... I read through the AGN post you linked and even "Scott" stated in that post that there may be "some cases" where higher mounts cause more cant errors. There can't be "some cases". It either happens or it doesn't. ...

That is true, and there are also "some cases" where higher scope mounts cause less "cant" errors.

When your POA does not match your intended POI, then errors resulting from cant will be affected by scope height. But is that really a cant error? I consider it an aiming error, the same as miss-ranging. True holdover (aiming above the intended POI) errors and ranging errors are both aiming errors, and both are affected by scope height. High scopes make both of them worse at closer range, and less at longer range.



If you are clicking-on or using vertical graduations on the reticle as holdover aim points, then scope height has no affect on gun cant errors. Gun cant errors are determined by cant angle and amount of projectile drop - and that's all.

Would the amount/effect of cant be decreased considerably by the trigger/grip/hand being, say, half the distance closer to the bore. 

Or am I way off on this thinking (as per most "thinking" I do"

No, though it could affect the error magnitude of a "pulled" shot.

If "clicking-on", then I agree with you 100%. I've never disagreed with that. The rest is not correct, IMO. With "aiming over", you eliminate "ranging error" by knowing exactly how much you need to "aim over". Is that a guess with a first shot? Probably. But focusing a scope to get a distance is also a guess. A much more precise one, but still a guess. 

At longer ranges, you might need to "aim over" 6 inches with a high scope and 1 foot with a low scope (just numbers as an example). But neither case results in a "ranging error" IF you know how much "aim over" is needed. If so, then you are "ranged" correctly, by definition. And using that method, INCREASING sight height results in INCREASING horizontal cant error with INCREASING distance, not less.

As to using the mil-dots for holdover, I am not as certain of the effect with that method but I will still say that I BELIEVE that it is the same as I've stated. This is WHY I believe it would be the same-

Take 2 identical rifles, same pellet, same velocity, same zero distance (assume 30 yards), but shooting with separate low and high scopes. Assume for example that the low setup needs 3 mils holdover to hit center at 90 yards and the high only needs 2 mils holdover to hit center at the same distance. Shoot the low setup uncanted with 3 mils holdover and hit center. No "ranging or aiming error". Cant 5 degrees CCW (as viewed from behind) and you shoot low and left. Still no "ranging or aiming error" as you were using the correct mil-dot to hit center but you canted, causing the miss. Now repeat with the higher mounted sight. Shoot uncanted with 2 mils holdover and hit center. Again, no "ranging or aiming error". Cant 5 degrees CCW as before and you hit further left and, I BELIEVE, slightly less low. WHY DO I BELIEVE THAT? Because the higher mounted sight has a steeper ANGLE of convergence of bore to LOS VERTICALLY to reach the common zero yardage. The holdovers (different but correct for each height for the longer distance) handles the vertical component needed for the shot to hit but the cant (remember, same angle in degrees of rotation for each) results in a steeper HORIZONTAL angle of projectile flight in relation to LOS because of the larger radius of the higher sight (LOS to bore) that was established for each by the common zero distance. That RADIUS does not change once mounted and the ANGLE of convergence does not either. That ANGLE of convergence (steeper vertically only for the higher sight when not canted but steeper both vertically and horizontally as well WHEN CANTED) is what continues beyond the zero distance (and changes from CONVERGENCE inside the zero distance to DIVERGENCE beyond) and widens with progressing distance as sight height increases. The vertical convergence (and any projectile rise above LOS beyond 30 yard zero distance as convergence angle changes to divergence angle) is opposed by gravity and gravity pulls the projectile back toward LOS. Horizontally, gravity DOES NOT pull the projectile back toward LOS. It only pulls it downward. That steeper angle of convergence toward LOS (actually DIVERGENCE once PAST the 30 yard distance) causes the projectile to move progressively left beyond the 30 yard mark. More so for the higher sight due to the scope mounts establishing the larger radius and resulting steeper angle.