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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Ballistics Question
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<blockquote data-quote="Bart B" data-source="post: 653367" data-attributes="member: 5302"><p>According to Shooter's website info on their software, it supports MOA, IPHY and Mils.</p><p></p><p>But in my tests of various scopes on a bench collimator accurately measuring adjustment values per click, they vary up to 5% or more. Even the same model for a given make their optical tolerances in focal length can add up to a 5% spread. If the focal length of a set of lenses is 5% more than spec (normal high end optical lens tolerance, both camera and telescope lenses), focusing the target on the reticule makes the image 5% bigger than the adjustment mechanics are set for. That ends up making the adjustments 5% smaller per click; 0.2375 instead of 0.2500 unit if the clicks are 1/4 unit per click. The mechanics of scope sight adjustments are set as close to the spec as manufacturing allows. Once set up, they cannot compensate for the tolerances in the scope's front end objective lens group tolerances.</p><p></p><p>If you want near zero tolerance in your numbers, better measure your scope's adjustments to the same accuracy.</p><p></p><p>There's about 4.7% difference between trig MOA's and shooting MOA's (inches per hundred yards). And a scope spec'd at 1/4 iphy per click may actually have 1/4 trig MOA.</p></blockquote><p></p>
[QUOTE="Bart B, post: 653367, member: 5302"] According to Shooter's website info on their software, it supports MOA, IPHY and Mils. But in my tests of various scopes on a bench collimator accurately measuring adjustment values per click, they vary up to 5% or more. Even the same model for a given make their optical tolerances in focal length can add up to a 5% spread. If the focal length of a set of lenses is 5% more than spec (normal high end optical lens tolerance, both camera and telescope lenses), focusing the target on the reticule makes the image 5% bigger than the adjustment mechanics are set for. That ends up making the adjustments 5% smaller per click; 0.2375 instead of 0.2500 unit if the clicks are 1/4 unit per click. The mechanics of scope sight adjustments are set as close to the spec as manufacturing allows. Once set up, they cannot compensate for the tolerances in the scope's front end objective lens group tolerances. If you want near zero tolerance in your numbers, better measure your scope's adjustments to the same accuracy. There's about 4.7% difference between trig MOA's and shooting MOA's (inches per hundred yards). And a scope spec'd at 1/4 iphy per click may actually have 1/4 trig MOA. [/QUOTE]
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