The Effects of Scope Cant

I must be missing something here (not totally unexpected)...if the shots in the article were off by ~9" at 600 with 5 degrees of cant, then by using simple math they'd miss by just under 2" at 300 with 2 degrees of cant.

Or does the math not work that way?
 
The math doesn't work that way. A flatter shooting gun will be affected less than one that requires more "come up" because that come up is steepening the upward trajectory, now tilt that rifle to the side and that "come up" is coming sideways too.
 
Farmer Harv said:
I must be missing something here (not totally unexpected)...if the shots in the article were off by ~9" at 600 with 5 degrees of cant, then by using simple math they'd miss by just under 2" at 300 with 2 degrees of cant.

Or does the math not work that way?
Click to expand...


The math doesn't work that way.

You can just use a ballistics program if you don't care for the math.

If you do care for the math, you take the amount of elevation on your sights (above boreline) and multiply it by the sine of the cant angle, which gives you the horizontal displacement of the bulet in MOA. You can then convert that to inches if needed.

So if at 300 you have (say) 6moa on your scope (over boreline) and 2 degrees of cant:
6*sin(2deg)=.21moa of offset to the side (which is 0.62")

if you're at 1000 and have 35moa of elevation, the same 2 degrees of cant gives:
35*sin(2deg)=1.2moa (12 inches) aide offset

The thing to note here is that at longer distances you have more elevation, plus at longer distances each minute is worth more inches. So the side deflection in minutes grows at a rate a bit faster than the distance, and in inches it grows a bit faster than the distance squared
 
Ahhh, there is much learning to be done here. Excellent. :)

However, after playing around on the JBM calculator (thanks for the link btw) I found that the simple math actually does work (maybe. see below). Not being able to come up with the same results as the article (not even close actually), I finally set the zero range to 600, and voila, it shows a 1.8" offset at 300 with 2 degrees of cant.

SS02.png



Here's the chart with the zero at 300. As rnbra-shooter stated... an offset of .08" (not sure why mine is .01" greater. Sight height maybe?).

SS03.png


Now the question is: Using the calculator why is the offset at 600 only 1.6" with a 300 zero, when it's 3.7" with a 600 zero? Elevation is ~17MOA either way (.58MOA offset doing the math), so is the calculator not working this part of the chart correctly? Or am I once again missing something?
 
anchor3593 said:
http://www.canadiangunnutz.com/forum/showthread.php?t=526208

The link to the other discussion.
Click to expand...

rnbra-shooter said:
I might be one of the people being thought of as a "naysayer" but I don't think that's necessarily true (what I was saying, and what I still say, is that in most cases a scope shooters doesn't need a bubble level rather his reticle alignment is good enough. And my other point was that the cant of the scope relative to the rifle is immaterial, the important factory is that the scope cant relative to the target level be kept consistent)
Click to expand...

Many of the people commenting on these threads don't seem to understand that there is more than one type of cant and that their effects are vastly different. If you believe that the experiment above illustrates the effects of cant between the rifle and the scope, you don't understand the different. (don't mean you rnbra-shooter, you clearly do)
 
Farmer Harv said:
Ahhh, there is much learning to be done here. Excellent. :)

However, after playing around on the JBM calculator (thanks for the link btw) I found that the simple math actually does work (maybe. see below). Not being able to come up with the same results as the article (not even close actually), I finally set the zero range to 600, and voila, it shows a 1.8" offset at 300 with 2 degrees of cant.
Click to expand...

Nice to see you gave it a try, and that you figured it out. It's a bit obscure but you found the "secret", which is that you have to set your zero range to the distance you are interested in (the 300, 600 that you did).


Now the question is: Using the calculator why is the offset at 600 only 1.6" with a 300 zero, when it's 3.7" with a 600 zero? Elevation is ~17MOA either way (.58MOA offset doing the math), so is the calculator not working this part of the chart correctly? Or am I once again missing something?
Click to expand...

Look at it again. In your 600yard screen shot it says "Elevation: 17.185 MOA", in the 300y screenshot it says "Elevation: 7.884MOA".

sin(2deg) * 17.185MOA = 0.6MOA (which agrees with the 600y screenshot)

sin(2deg) * 7.884MOA = 0.275MOA (the 300y screenshot shows 0.2MOA; I would have thought that it should round rather than truncate)
 
kombayotch said:
Many of the people commenting on these threads don't seem to understand that there is more than one type of cant and that their effects are vastly different. If you believe that the experiment above illustrates the effects of cant between the rifle and the scope, you don't understand the different. (don't mean you rnbra-shooter, you clearly do)
Click to expand...

+1. Geometry is simple, but some people cling obsessively to their ignorance.
 
Ahhh, ok. I'm getting it. I think the biggest thing with the charts is to ignore the charts, and just do the math for the specific range you're shooting at.

I put my iPhone with a level app on the rail, and was a bit surprised to see how easy it was to get to 1.5 degrees of cant without any external references. It became progressively more noticeable from there up, and 5 degrees felt like a Lot of tilt. This was on level/flat ground though, and tomorrow I hope to try this on some sloped surfaces. I can already see the utility of a bubble level when there are no horizontal/vertical lines to go by, and though the offset may not be that great, my less than elite shooting skillz can use all the help they can get. :)
 
Farmer Harv said:
Ahhh, ok. I'm getting it. I think the biggest thing with the charts is to ignore the charts, and just do the math for the specific range you're shooting at.

I put my iPhone with a level app on the rail, and was a bit surprised to see how easy it was to get to 1.5 degrees of cant without any external references. It became progressively more noticeable from there up, and 5 degrees felt like a Lot of tilt. This was on level/flat ground though, and tomorrow I hope to try this on some sloped surfaces. I can already see the utility of a bubble level when there are no horizontal/vertical lines to go by, and though the offset may not be that great, my less than elite shooting skillz can use all the help they can get. :)
Click to expand...

BTW here's a rifle range where the topography conspires against you getting a good level reference.
image003a.jpg
 
Wow. I never would have guessed that would cause that much difference. Really good to see. Very good test/demonstration. Thanks for sharing.
 
Farmer Harv said:
I can already see the utility of a bubble level when there are no horizontal/vertical lines to go by, and though the offset may not be that great, my less than elite shooting skillz can use all the help they can get. :)
Click to expand...

You're in SK though. That's one big level reference. You should be good.:D
 
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