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Line of Sight - Line of Bore Qn.

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Line of Sight - Line of Bore Qn.

Old 10-17-2008, 08:49 AM
  #1  
Nontypical Buck
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Default Line of Sight - Line of Bore Qn.

OK, I'm having a brain cramp.

We know that the line of the bore must be angled upward (however slightly)in relation to the line of sight, in order for the bullet to hit the point of aim. We know that the bullet will cross the line of sight twice, once about 25 yds from the gun, and again some distance downrange. I get this part.

Here's the question. When shooting with a scope, where does thisangle come from? Scope mounts seem interchangeable front to back (or should be), so that's not it. Doesn't seem like guns are manufactured to provide this angle in the scope mounting area. So that leaves the scope itself. I can believe that, but I guess I don't know enough about how scopes work to understand it.

Can anyone explain how a scope provides this angle between the line of sight and the line of the bore, and how it can actually be adjusted to change the angle? When you adjust the crosshairs, are you actually adjusting the angle that the scope is "looking"? How is that achieved?
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Old 10-17-2008, 08:54 AM
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Default RE: Line of Sight - Line of Bore Qn.

It is just the difference in the height the scope is above the barrel. The only way to adjust it is having a lower or higher mounted scope. With see though bases that you can use the open sights with is a good example. The scope will be sitting much higher and the angle between the barrel and scope will be much more. This is also combined with the balistics of the load that you are shooting which creates the arced path of the bullet.
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Old 10-17-2008, 09:38 AM
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Default RE: Line of Sight - Line of Bore Qn.

Nope. That's not where the angle comes from. The scope could be two feet above the barrel, and the angle between the bore and the scope (adjusted toits optical center) would be the same. It would have a dramatic effect on the angle needed to sight in for a given distance though. I'm really asking how does adjusting the scope change that angle? What are the parts in the scope that are being moved?
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Old 10-17-2008, 09:52 AM
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Default RE: Line of Sight - Line of Bore Qn.

The angle you are referring to is the difference between the line of sight and the line of the bore. I've had trouble trying to explain this to the old timers who refused to believe that the bullet starts to drop the second it leave the bore. They were convinced that the bullet rises when it leaves the bore. And I told them that is because the bore is slightly pointed up just the way you described.
Now, from what I recall, the rifle scope has mirrors and prisms inside, when you adjust the scope you are actually rotating these mirrors. This is why your reticle is always centered. I believe the mirrors or prisms are held in place by opposing springs allowing for up/down, left/right adjustment. So to answer your question, the angle comes from inside the scope.
If sure if I am wrong, I will get jumped on.
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Old 10-17-2008, 10:07 AM
  #5  
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Default RE: Line of Sight - Line of Bore Qn.

bronko22000
Consider your self it, high powered scopes like spotting scopes use mirrors and prisms for the most part normal rifle scopes are straight through,though there are a few targetor varmint rifle scopes that are an exception.
UncleNorby
If I understand your question correctly this is the answer.
scopes have a octagonal ring which is adjusted by the windage and elevation adjustments in which the cross hairs are mounted this moves the cross hairs around on the seen you see when you look through the scope. It actually works some thing like your back sight. Hope this helps. Lee
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Old 10-17-2008, 10:10 AM
  #6  
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Default RE: Line of Sight - Line of Bore Qn.

You are saying exactly what I as thinking, just did not know if it was true. I never really gave it a lot of thought before. I guess I thought that the crosshairs were moving up/down and left/right with adjustments. Then I got thinking about it and that really did not make sense, or account for the angle issue.

Do others agree or know that the scope adjustments are actually rotating mirrors, lenses, or even prisms?

I'd really like to see a picture of the guts of a scope and how the adjustments work. Anybody know where I could find one?
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Old 10-17-2008, 10:24 AM
  #7  
Nontypical Buck
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Default RE: Line of Sight - Line of Bore Qn.

This from a website:

Mechanics
The inner workings of a scope have a direct affect on shooting accuracy. As adjustments are made during sight-in, the cam tube, which holds the reticle and lenses in place, moves inside the scope. To stay on target and produce a quality image, this tube must be strong enough to absorb the impact of heavy recoil during shooting and remain in place. When selecting your riflescope look for precision (positive) adjustments, point-of-impact consistency, reticle strength and waterproof, fogproof and shockproof durability. You'll also want to consider weight, bulk and ergonomics, which are especially important during long days in the field.


So there is this cam tube thing that moves inside the scope. If that's tru,I can see how it could be angled up and down or left/rightto varying degrees. Starting to make sense.
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Old 10-17-2008, 11:03 AM
  #8  
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Default RE: Line of Sight - Line of Bore Qn.










http://www.shootingtimes.com/optics/meade_101705/index.html
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Old 10-17-2008, 03:28 PM
  #9  
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Default RE: Line of Sight - Line of Bore Qn.

UncleNorby

Do others agree or know that the scope adjustments are actually rotating mirrors, lenses, or even prisms?
New scopes certainly work that way - I still have to old weaver K4's that the cross hairs do move in.... seems really odd when you look throught the scope and the cross hairs are off in the corner....

Remember some of the arly Bausch and Lomb scope did not even have turrents - you had to buy adjustable rings...
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Old 10-20-2008, 07:07 AM
  #10  
Nontypical Buck
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Default RE: Line of Sight - Line of Bore Qn.

All great info. Thanks.
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