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Old 14th October 2015, 09:16 AM
skires skires is offline
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Join Date: Apr 2009
Posts: 950

Originally Posted by hmangphilly View Post
would that crossover be avoided if you aimed (zero'd ) (adjusted windage ) 1mm off at all ranges ?
or am i having a moment ?
Er ... I think you are having a slight moment?

As I understand it if the scope isn't in perfect line with the breech/barrel then you will be bang on zero at your chosen zero range. You have zeroed that range for elevation and windage. However, at distances a good way away from your zero you will firstly ( close range ) impact on one side of the vertical, and then at the other extreme range from your zero ( furthest range ) you will impact on the other side of the vertical.

Hence the term "Crossover". You poi's will actually cross over your vertical and will only be bang on horizontal zero at the range that you zeroed the windage on the scope.

I've read a bit on this re airguns and a formula I once saw ( I think ) was actually showing that the scope can be quite a bit out of line with the barrel and the crossover error was still very very minimal at airgun ranges. There was a far far greater chance of any off horizontal error at various ranges being due to light cant of the rifle or the cross hair being slightly off perfect vertical ( or, of course, PA error due to eye misalignment with a set distance focus ).

So I'm not sure it's a problem to begin with.

So, theoretically, although the scope is only 1mm off centre to the bore ( horizontally ) it will hold zero at your zero range ( say 35 yards ... because you've set it at that ) but at 55 yards it may be several mm's off. Similarly ... but on the other side ... it may be several mm's off at very close range. So if you try and adjust the windage turret to compensate for the very close ones ... you will now be off at your 35 yard zero ... and even further off at your max distance.

Is that what you meant? Sorry if that's a Granny and her eggs post.

Last edited by skires; 14th October 2015 at 09:50 AM.
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