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Size of target at 800 yards? And how close to center?

 
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  #15  
Old 10-09-2013, 09:10 PM
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Re: Size of target at 800 yards? And how close to center?

A couple of thoughts -

It's not possible for a flexible rope to hang diagonally unless there is some lateral force being exerted on it (such as wind). Any torque that is generated by the block being off center will simply bend the rope at the point of least resistance (right next to the block), and the rope will end up being plumb.

Canting the scope to compensate for spin drift isn't a bad idea. Spin drift and scope cant both have a parabolic effect on POI and the curves are pretty similar, although they do start to diverge after 1500 yards or so. You'd need somewhere around 2 degrees of clockwise cant on the scope. For simplicity it would probably be best to mount the scope straight, in line with the bore centerline, and then rotate your scope level 2 clockwise. You could use the posterboard technique to get the scope mounted square to the gun and then draw a 2 line (or whatever angle you figure) to make the adjustment to your level.
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  #16  
Old 10-09-2013, 11:56 PM
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Re: Size of target at 800 yards? And how close to center?

Quote:
Originally Posted by sdriverbottom View Post
This might be a stupid question but I have seen this on one of the long range hunting shows..they put a cant in the scope to take out spin drift. With now when my action is level as pics showed my crosshairs off center counter clockwise a bit (so there moving down and right when dialing long range) With my cross hairs off counter clockwise I offset that by rotating clockwise to level on my scope. This in turn rotates my level bore to cant clockwise ( when I shoot with that set up my hits are left of target, does that seem right with impacts??

Because what I'm wondering for the time being level my action ( scope is cant counter clockwise) move my level on my scope to match my bore..so spin drift is to the right but scope is offsetting that with it mounted counter clockwise and moving up and left, then maybe the bullet meets in the middle??

Thought it was worth asking since I'm sure I saw it once, then during offseason get things squared up.
There simply is no way to accurately cant your scope purposely to take out spin drift with any accuracy at all.

Whomever is suggesting attempting to do so is trying to sell you a wagon load of BS.

That is why we have ballistic calculator apps for just about every electronic device on the market today. You would be better off simply guessing at spin drift and holding a little more left than attempting to eliminate it by canting the scope.
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  #17  
Old 10-10-2013, 07:09 AM
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Re: Size of target at 800 yards? And how close to center?

Quote:
Originally Posted by el matador View Post
A couple of thoughts -

It's not possible for a flexible rope to hang diagonally unless there is some lateral force being exerted on it (such as wind). Any torque that is generated by the block being off center will simply bend the rope at the point of least resistance (right next to the block), and the rope will end up being plumb.
After thinking about it, this is right. The block will center it's gravity on the rope so the problem is not induced by a canted rope.

I agree that canting the scope to account for spin drift is not a good idea.
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  #18  
Old 10-10-2013, 08:40 AM
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Re: Size of target at 800 yards? And how close to center?

Thanks for the advice guys! Sounds like I better level my scope now instead of waiting till after the season.
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  #19  
Old 10-10-2013, 02:30 PM
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Re: Size of target at 800 yards? And how close to center?

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Originally Posted by WildRose View Post
There simply is no way to accurately cant your scope purposely to take out spin drift with any accuracy at all.
Can you expound upon this a little? Also wondering if it's your opinion or if you can cite some facts or data to illustrate why it can't be done "with any accuracy at all". I am only looking at charts and equations, and I think it looks like a very viable solution. Many shooters will sight in a little bit left to offset the effects of spin drift out to 700 yards or so, and that's using a straight line of sight to offset a parabolic curve. Clearly those paths would diverge sooner than if you matched one parabolic curve to another. I'm not trying to be argumentative, just saying that the data I see makes it look like a good idea. I want to learn as much as I can from everyone here and I would welcome any experiences or calculations that refute the data I've come up with. I'm attaching some numbers from the ballistics calc.

Now I realize that spin drift will vary slightly with changes in air density, but out to 1200 yards those changes only amount to a couple of inches.
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Size of target at 800 yards? And how close to center?-cantspin.png  
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  #20  
Old 10-10-2013, 03:43 PM
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Re: Size of target at 800 yards? And how close to center?

Quote:
Originally Posted by el matador View Post
Can you expound upon this a little? Also wondering if it's your opinion or if you can cite some facts or data to illustrate why it can't be done "with any accuracy at all". I am only looking at charts and equations, and I think it looks like a very viable solution. Many shooters will sight in a little bit left to offset the effects of spin drift out to 700 yards or so, and that's using a straight line of sight to offset a parabolic curve. Clearly those paths would diverge sooner than if you matched one parabolic curve to another. I'm not trying to be argumentative, just saying that the data I see makes it look like a good idea. I want to learn as much as I can from everyone here and I would welcome any experiences or calculations that refute the data I've come up with. I'm attaching some numbers from the ballistics calc.

Now I realize that spin drift will vary slightly with changes in air density, but out to 1200 yards those changes only amount to a couple of inches.
Impact deviation due to cant is dependent upon where you zero If you zero @ 100 the impact deviation @ 1000 will be greater than if you zero @ 200 or 300.

If you zero @ 200 there will be no impact deviation @ 200 because you are zeroed there. POI and POA are the same. Deviation will begin after the zero point. I believe it would be impossible to align the spin drift and cant curves.

Also, there are different types of cant errors such as cant with bore and wingage reticle aligned and cant when bore and windage reticle is not aligned.
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  #21  
Old 10-10-2013, 03:51 PM
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Re: Size of target at 800 yards? And how close to center?

Quote:
Originally Posted by el matador View Post
Can you expound upon this a little? Also wondering if it's your opinion or if you can cite some facts or data to illustrate why it can't be done "with any accuracy at all". I am only looking at charts and equations, and I think it looks like a very viable solution. Many shooters will sight in a little bit left to offset the effects of spin drift out to 700 yards or so, and that's using a straight line of sight to offset a parabolic curve. Clearly those paths would diverge sooner than if you matched one parabolic curve to another. I'm not trying to be argumentative, just saying that the data I see makes it look like a good idea. I want to learn as much as I can from everyone here and I would welcome any experiences or calculations that refute the data I've come up with. I'm attaching some numbers from the ballistics calc.

Now I realize that spin drift will vary slightly with changes in air density, but out to 1200 yards those changes only amount to a couple of inches.
Without your scope tube and rings being calibrated and marked you are just guessing and approximating the cant.
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