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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Canting - the right answer
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<blockquote data-quote="JBM" data-source="post: 110542" data-attributes="member: 1969"><p>[ QUOTE ]</p><p></p><p>My previous post was addressing this issue (as posted by Tirofijo):</p><p> [ QUOTE ]</p><p> But when you have a hunting rifle you don't normally change the scope's settings, so you may take a shot at 400 m even if your zero is 200 m using holdovers. In this case the angle between LOS and bore line corresponds to the 200 m zero and the effect of canting would be smaller than if the rifle was zeroed at 500. </p><p></p><p>[/ QUOTE ] </p><p></p><p>To which the short answer is 'No!!!!!' /ubbthreads/images/graemlins/shocked.gif /ubbthreads/images/graemlins/smile.gif for all the reasons given in my previous post. </p><p></p><p>As soon as you apply holdover you are, in effect, re-zeroing to the new target range.</p><p></p><p></p><p>[/ QUOTE ]</p><p></p><p>Maybe we're agreeing here, but I don't think so. Zeroing is defined as where the bullet crosses the line of sight. If you hold over this doesn't change so holding over doesn't change the zero. It also doesn't change the angle between the bore and the line of sight -- the cause of the canting error.</p><p></p><p>[ QUOTE ]</p><p></p><p>The error of reasoning here is based in the fact that people have fixated on the angle between the boreline and the 'zeroed at X yds scope'. </p><p></p><p></p><p>[/ QUOTE ]</p><p></p><p>Because that is what causes the cant error. You're rotating the firearm around the line of sight. It's the angle relative to the line of sight that causes the error.</p><p></p><p>[ QUOTE ]</p><p></p><p>When you are hitting a target at a given range; the critical angle for the purposes of cant effect calculations is:</p><p></p><p>[boreline's elevation relative to a horizontal datum (ie its Quadrant Elevation)] MINUS [True Angle of Sight to the Target (ie AS)] = Tangent Elevation [The tangent Elevation being that part of the QE that has been applied to account for the bullet's drop at that distance.]</p><p></p><p></p><p>[/ QUOTE ]</p><p></p><p>Are you defining the Tangent Elevation as the angle between the bore and the line of sight? If so I agree. If not, please derive this and post it somewhere so we can see it.</p><p></p><p>[ QUOTE ]</p><p></p><p>You all (not Bart!) need 'Red Leg' [a US term that I know won't require transatlantic translation! /ubbthreads/images/graemlins/smile.gif] advice; not more formulae /ubbthreads/images/graemlins/smile.gif /ubbthreads/images/graemlins/smile.gif </p><p></p><p></p><p>[/ QUOTE ]</p><p></p><p>Yeah. Heaven forbid we should understand what is going on.</p></blockquote><p></p>
[QUOTE="JBM, post: 110542, member: 1969"] [ QUOTE ] My previous post was addressing this issue (as posted by Tirofijo): [ QUOTE ] But when you have a hunting rifle you don't normally change the scope's settings, so you may take a shot at 400 m even if your zero is 200 m using holdovers. In this case the angle between LOS and bore line corresponds to the 200 m zero and the effect of canting would be smaller than if the rifle was zeroed at 500. [/ QUOTE ] To which the short answer is 'No!!!!!' [img]/ubbthreads/images/graemlins/shocked.gif[/img] [img]/ubbthreads/images/graemlins/smile.gif[/img] for all the reasons given in my previous post. As soon as you apply holdover you are, in effect, re-zeroing to the new target range. [/ QUOTE ] Maybe we're agreeing here, but I don't think so. Zeroing is defined as where the bullet crosses the line of sight. If you hold over this doesn't change so holding over doesn't change the zero. It also doesn't change the angle between the bore and the line of sight -- the cause of the canting error. [ QUOTE ] The error of reasoning here is based in the fact that people have fixated on the angle between the boreline and the ‘zeroed at X yds scope’. [/ QUOTE ] Because that is what causes the cant error. You're rotating the firearm around the line of sight. It's the angle relative to the line of sight that causes the error. [ QUOTE ] When you are hitting a target at a given range; the critical angle for the purposes of cant effect calculations is: [boreline’s elevation relative to a horizontal datum (ie its Quadrant Elevation)] MINUS [True Angle of Sight to the Target (ie AS)] = Tangent Elevation [The tangent Elevation being that part of the QE that has been applied to account for the bullet’s drop at that distance.] [/ QUOTE ] Are you defining the Tangent Elevation as the angle between the bore and the line of sight? If so I agree. If not, please derive this and post it somewhere so we can see it. [ QUOTE ] You all (not Bart!) need 'Red Leg' [a US term that I know won't require transatlantic translation! [img]/ubbthreads/images/graemlins/smile.gif[/img]] advice; not more formulae [img]/ubbthreads/images/graemlins/smile.gif[/img] [img]/ubbthreads/images/graemlins/smile.gif[/img] [/ QUOTE ] Yeah. Heaven forbid we should understand what is going on. [/QUOTE]
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Canting - the right answer
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