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Buble level anti cant device
- Thread starter GQ
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I'll eventually find one, and hopefully reasonably priced 
Thank you to both of you guys."broekzwans"
"Scotchmo"@broekzwans,
When you cant the gun, while holding on target:
The bore line (dashed cyan line) is not the cant axis. NO
The parallel lines of the scope above the bore (dashed orange and green lines) are not the cant axis. NO
The cant axis is the line of sight to the center of the target (solid orange and green lines). YES
(trajectory compressed in x-axis to fit screen):
I already see where our stories are mismatching. We're both right, we're just looking at it a different way. Maybe I had to write this clearer but the dots I've used in the calculation above are the start of the line of sight and the placement of the bore at that amount of cant. With the angling plots I'm looking at the tip of the muzzle towards the target.
Your story holds if the canting axis is right in between the two scopes, in that case the scope height doesn't matter and will give the same spread from canting. If we move the first scope to 1 cm and the second scope to 11 cm there is still no change. You're completely right in this!
If we look at three different swiveling points I think it'll be clear. In the following I've added an extra dot, a red one, this will depict the center between the two scopes.
The first situation: center of my canting axis is the line of sight from the 10 cm scope
The second situation: the center of my cant axis is the center between the two scopes
For the record: added the 1 cm and 11 cm scope height into the picture for extra clarity
The third situation: The center of my cant is the line of sight from the 2cm scope
As you can see above, when we chose the center of the scopes as canting axis both scopes move an equal amount from the bore which causes no impact shift between the two scopes. If we look at the total displacement of the bore compared to the cant axis you can see that the horizontal barrel misalignment becomes larger with an increasing scope height.
For the record: I'm not trying to burn you or trying to be a smart ass, I'm just trying to get us on the same page
Now we can figure out what is true.
Regards
GQ
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broekzwans,
When we cant a gun, we are still keeping the line of sight pointed directly on the bullseye. Any scope mounted on that gun, regardless of height, regardless of the amount of cant, still has the LOS pointed at the bullseye. All of your colored dots that depict the LOS for different scope heights, should all intersect the target at it's center.
The point of impact is what moves off the bullseye.
The bore line is a straight line unaffected by the direction of gravity. You should show the trajectory. Gravity is normally a Y component. It has both X and Y components relative to a canted gun. Show the affects of gravity on the trajectory in your diagrams.
The LOS always stays on target. Concentrate on what is happening to the trajectory relative to the canted gun. The trajectory is what is changing.
Here is a demo that shows mostly what I'm saying:
http://www.arld1.com/targetplottrajectory3.html
When you cant the gun at all angles, you form a circular impact pattern. The pattern is formed by plotting the following XY coordinates for various cant angles:
X = drop x sin(angle)
Y = drop x (1-cos(angle))
Bottom line - mount the scope at whatever height suits you. Cant the gun as little as possible.
When we cant a gun, we are still keeping the line of sight pointed directly on the bullseye. Any scope mounted on that gun, regardless of height, regardless of the amount of cant, still has the LOS pointed at the bullseye. All of your colored dots that depict the LOS for different scope heights, should all intersect the target at it's center.
The point of impact is what moves off the bullseye.
The bore line is a straight line unaffected by the direction of gravity. You should show the trajectory. Gravity is normally a Y component. It has both X and Y components relative to a canted gun. Show the affects of gravity on the trajectory in your diagrams.
The LOS always stays on target. Concentrate on what is happening to the trajectory relative to the canted gun. The trajectory is what is changing.
Here is a demo that shows mostly what I'm saying:
http://www.arld1.com/targetplottrajectory3.html
When you cant the gun at all angles, you form a circular impact pattern. The pattern is formed by plotting the following XY coordinates for various cant angles:
X = drop x sin(angle)
Y = drop x (1-cos(angle))
Bottom line - mount the scope at whatever height suits you. Cant the gun as little as possible.
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I give broekzwans credit for making the attempt. And the confidence in his work. But a young engineering student (been there) still has things to learn (actually, we all do). Mechanical engineers often need to account for gravity in their work. Not so sure about electrical engineers.
Here's how it is, simplified, graphically (from a semi-retired, professional, mechanical engineer - me):
All canted impacts will lie on the circle of radius=DROP. With the 12 O'clock position of the circle at the aim point.
Here's how it is, simplified, graphically (from a semi-retired, professional, mechanical engineer - me):
All canted impacts will lie on the circle of radius=DROP. With the 12 O'clock position of the circle at the aim point.
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I completely agree with you on the 360 degrees of spread you going to get when canting around the LOS. I'm also fully aware that gravity starts to kick in at the moment the pellet/bullet leaves the barrel.
What I'm trying to show with my graphs is that the point where the pellet will start flying (the misalignment of scope and barrel) will change more when the scope height increases when canted. I believe that the increased misalignment of a higher placed scope on the same cant angle will affect the trajectory in a non-beneficial way.
So yes, all scopes, no matter at what height mounted, will have the same reference point on the target (the bulls-eye). But depending on which scope/LOS you will choose as canting axis will increase or decrease the size of the 360 degree ring in your post, higher -> larger, lower -> smaller.
So the LOS is the canting axis and the trajectory is crossing this line (twice if target is after the apex and there is no cant). Like I mentioned in the my first calculation post I believe that the trajectory will swivel around the first crossing point of the trajectory with the LOS. Why I believe this happens: At the start the trajectory is a pretty much straight/linear line because gravity needs time to increase it's effect ( ~10 m/s^2) on the pellet. When the trajectory crosses with the LOS, the trajectory is still pretty much linear. To have an intersection with both lines one of them has to point upwards or the other one has to point downwards. A target is in most cases approximately at the same height as the shooter so we can take the LOS as the fixed axis. Because they're both (near to) linear at the start of the trajectory this point will remain pretty constant during a 360 degree cant.
Black is the barrel and trajectory and Red is the LOS. (sorry for the crappy trajectory curves, visio sucks at this )
The main thing I'm missing is in your explanation is a changing LOS height compared to trajectory, which is what happens when I increase my scope height.
When I shoot with a 5 degree canted rifle with a 2 cm high scope as canting axis I get a certain deviation, after shooting I look through the 10 cm high scope and I see the exact same deviation and both scopes are on the bulls-eye of the target. (which is logical of course)
After that I'm going to shoot a new group but then use the 10 cm high scope, also canted at 5 degrees, as canting axis and find a certain deviation. When I then look through the 2 cm high scope the deviation is the same as viewing through the 10 cm scope and both scopes are still on the bulls-eye. (which is also logical of course)
But what I don't believe is that both the deviations are at the exact same distance from the bulls-eye, simply because the amount the bore will deviate from the canting axis is completely different and therefore my trajectory is different. Both in the vertical and the horizontal plane. This tiny part is what I think is missing in your explanation.
I will test this to try to prove this theory but first the weather has to calm down here, .22 pellets and wind isn't a great combination for testing purposes in the outdoors. I have a scope which can be placed approximately 4 cm above the bore and one that I have placed almost 6 cm above the bore.
The problem with us engineers is that discussing is part of the job and most of 'm really like to do it So sorry for the rest if this is starting to get boring, we're not fighting, just comparing theories and trying to find where one of us goes wrong at some point So Scotchmo, thanks for holding on and bringing in knowledge because a discussion with calculations/knowledge/facts (or what we think are facts ) is what we need to find out what's the right way
What I'm trying to show with my graphs is that the point where the pellet will start flying (the misalignment of scope and barrel) will change more when the scope height increases when canted. I believe that the increased misalignment of a higher placed scope on the same cant angle will affect the trajectory in a non-beneficial way.
So yes, all scopes, no matter at what height mounted, will have the same reference point on the target (the bulls-eye). But depending on which scope/LOS you will choose as canting axis will increase or decrease the size of the 360 degree ring in your post, higher -> larger, lower -> smaller.
So the LOS is the canting axis and the trajectory is crossing this line (twice if target is after the apex and there is no cant). Like I mentioned in the my first calculation post I believe that the trajectory will swivel around the first crossing point of the trajectory with the LOS. Why I believe this happens: At the start the trajectory is a pretty much straight/linear line because gravity needs time to increase it's effect ( ~10 m/s^2) on the pellet. When the trajectory crosses with the LOS, the trajectory is still pretty much linear. To have an intersection with both lines one of them has to point upwards or the other one has to point downwards. A target is in most cases approximately at the same height as the shooter so we can take the LOS as the fixed axis. Because they're both (near to) linear at the start of the trajectory this point will remain pretty constant during a 360 degree cant.
Black is the barrel and trajectory and Red is the LOS. (sorry for the crappy trajectory curves, visio sucks at this
)The main thing I'm missing is in your explanation is a changing LOS height compared to trajectory, which is what happens when I increase my scope height.
When I shoot with a 5 degree canted rifle with a 2 cm high scope as canting axis I get a certain deviation, after shooting I look through the 10 cm high scope and I see the exact same deviation and both scopes are on the bulls-eye of the target. (which is logical of course)
After that I'm going to shoot a new group but then use the 10 cm high scope, also canted at 5 degrees, as canting axis and find a certain deviation. When I then look through the 2 cm high scope the deviation is the same as viewing through the 10 cm scope and both scopes are still on the bulls-eye. (which is also logical of course)
But what I don't believe is that both the deviations are at the exact same distance from the bulls-eye, simply because the amount the bore will deviate from the canting axis is completely different and therefore my trajectory is different. Both in the vertical and the horizontal plane. This tiny part is what I think is missing in your explanation.
I will test this to try to prove this theory but first the weather has to calm down here, .22 pellets and wind isn't a great combination for testing purposes in the outdoors. I have a scope which can be placed approximately 4 cm above the bore and one that I have placed almost 6 cm above the bore.
The problem with us engineers is that discussing is part of the job and most of 'm really like to do it
So sorry for the rest if this is starting to get boring, we're not fighting, just comparing theories and trying to find where one of us goes wrong at some point So Scotchmo, thanks for holding on and bringing in knowledge because a discussion with calculations/knowledge/facts (or what we think are facts ) is what we need to find out what's the right wayUpvote 0
The wind lay down so I immediately went outside to test the above. I have to say, @Scotchmo, you were right! A slight but, this only holds for a certain range where the scopes will be zeroed on.
The setup I did the test with:
The bipod is able to cant 20 degrees to both sides, the table is canted about 5 degrees to the right so I could cant 15 degrees to the left and 25 degrees to the right. The scope in the picture is my Meopta, it's mounted 6 cm above the bore, the other scope I used is a bushnell that's mounted 4 cm above the bore. I've used the same rifle, speed and tube pressure (had a 160 bar CF bottle attached with the valve opened). The distance was 50 meters with a slight wind that picked up at some moments but nothing shocking.
To show that the cant is equal for the sake of fair testing a picture of the amount of cant:
Bushnell:
Meopta:
The result:
zoomed in on both and including measurements:
Bushnell:
Meopta:
This is with a cant of 15 degrees to the left, I also shot the 25 degrees to the right but the results were not clear enough to put in this post since half of the shots disappeared to outside the paper.
There is a difference of the average cant error of 2 mm ( Meopta had 37.5 mm and Bushnell had 35.5 mm) but this is insignificant since the weather had a slight play in this too.
But watch out, this phenomena only holds for shooting on the distance where you've zeroed your rifle. For further distances with the initial zero at the same point a higher scope will have worse effects of cant and for distances closer than the initial zero a higher scope is beneficial.
For more information it is beneficial to read this article: http://www.szottesfold.co.uk/2012/03/high-scope-and-canting-end-of-ancient.html
I found out where the error in my theory was, I assumed the crossing point of the LOS with the trajectory would be causing an increasing error for higher placed scopes. This sort of holds for distances further than the initial zero but the axis that's causing the increase isn't the crossing of the LOS with the trajectory but the difference in the bore line, the impact point and the added difference of the LOS with the trajectory.
So again, @Scotchmo thanks for holding on in this discussion, I've learned something and I think I'm not the only one
So to conclude what effects the cant error:
For a fixed distance:
- The canting angle
- The bullet drop at that range
For variable distances outside of the zero:
- The canting angle
- The bullet drop at that range
- The height of the scope
The setup I did the test with:
The bipod is able to cant 20 degrees to both sides, the table is canted about 5 degrees to the right so I could cant 15 degrees to the left and 25 degrees to the right. The scope in the picture is my Meopta, it's mounted 6 cm above the bore, the other scope I used is a bushnell that's mounted 4 cm above the bore. I've used the same rifle, speed and tube pressure (had a 160 bar CF bottle attached with the valve opened). The distance was 50 meters with a slight wind that picked up at some moments but nothing shocking.
To show that the cant is equal for the sake of fair testing a picture of the amount of cant:
Bushnell:
Meopta:
The result:
zoomed in on both and including measurements:
Bushnell:
Meopta:
This is with a cant of 15 degrees to the left, I also shot the 25 degrees to the right but the results were not clear enough to put in this post since half of the shots disappeared to outside the paper.
There is a difference of the average cant error of 2 mm ( Meopta had 37.5 mm and Bushnell had 35.5 mm) but this is insignificant since the weather had a slight play in this too.
But watch out, this phenomena only holds for shooting on the distance where you've zeroed your rifle. For further distances with the initial zero at the same point a higher scope will have worse effects of cant and for distances closer than the initial zero a higher scope is beneficial.
For more information it is beneficial to read this article: http://www.szottesfold.co.uk/2012/03/high-scope-and-canting-end-of-ancient.html
I found out where the error in my theory was, I assumed the crossing point of the LOS with the trajectory would be causing an increasing error for higher placed scopes. This sort of holds for distances further than the initial zero but the axis that's causing the increase isn't the crossing of the LOS with the trajectory but the difference in the bore line, the impact point and the added difference of the LOS with the trajectory.
So again, @Scotchmo thanks for holding on in this discussion, I've learned something and I think I'm not the only one
So to conclude what effects the cant error:
For a fixed distance:
- The canting angle
- The bullet drop at that range
For variable distances outside of the zero:
- The canting angle
- The bullet drop at that range
- The height of the scope
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Wow , this is very interesting guys.
Thank you very much to spend your time and share.
Regards
GQ
Thank you very much to spend your time and share.
Regards
GQ
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These prices I can stand: Levels and Pointers[/QUOTE]https://trenieroutdoors.com/gear/levels-and-pointers/embed/
Thurmond
Thurmond
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The problem I had with the hawke bubble level is that it's made for 9-11 mm and my rail is 11 mm. If you use them on an 11 mm rail they will start to climb upwards when tightening. Therefore I don't use them anymore..
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Edit: szottesfold and broekwans are correct for some specific instances when using aim points other than the bullseye as a means of drop compensation. Ignore what I said below.
You're on track now. The info in that szottesfold link is mostly good. His number 1. conclusion is right on. His number 2. conclusion is almost correct but backwards (as is yours).
Corrected szottesfold:
2. If we do the correction outside the scope (i.e. we have zeroed the rifle at a given distance and then shoot at another target with a holdover which is measured at the target), the canting error can be different – more or less – with the higher scopes. It will be less(not more) if the new range is greater than the zero range and more(not less) if it's shorter.
When doing that you have introduced holdover cant. That error is directly related to the amount of holdover used and the degree of cant. You can eliminate that possibility. Don't use holdover which is measured at the target. Instead, use mil-dots as holdover/aim points on a correctly mounted scope. When using the mil-dots for holdover, scope height or being outside zero does not matter. Only the amount of drop and the degree of cant.
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I never liked that type of scope level. I used one once, and there was no way to adjust it. If they end up in line with the scope-bore, you got lucky. I use levels that are mounted to a ring on the scope that can be rotated to achieve alignment.
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I always think of Ted's scope he had mounted at one of the Pyramid air events. Look at the ad at the top of the page to see how many risers Ted had mounted on his rifle. I don't think his rifle can "cant" without hitting the guys target beside him.
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I re-canted some things I said in my last post. It is possible to come up with some specific instances where scope height could affect cant. Unusual circumstances. Not normally encountered but possible. In most cases of cant error, scope height does not matter.
some things I said in my last post. It is possible to come up with some specific instances where scope height could affect cant. Unusual circumstances. Not normally encountered but possible. In most cases of cant error, scope height does not matter.Upvote 0
I believe the US Optics are a better product than the hawkes
that's one of the reasons I was looking for the US optics bubble level but I guess it's sold out everywhere and if I recall correctly I've read somewhere that the next shipment will be around september somewhereUpvote 0
You can get one from Canada."broekzwans"
I believe the US Optics are a better product than the hawkes
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Here is what I got out of this discussion! @broekzwans has the coolest looking bipod I have ever see. Could we have the brand name for it?
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Looks like an F-class (long range/high power) centerfire bipod. I wouldn't know the brand Rules say it must be attached to gun and be included in the weight limit. I used an attached Harris style bipod in FT Hunter Division during 2013 and 2014. I thought about using an F-class bipod. FT rules were changed in 2015, and it was no longer allowed.
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