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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Need help understanding why my ballistics calculator is doing this!!
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<blockquote data-quote="Bart B" data-source="post: 568252" data-attributes="member: 5302"><p>In the shooting sports here in the USA, they're both the same. That came to be long ago when both smallbore and highpower target rings were spaced in even inches apart.</p><p></p><p>That was established over a hundred years ago when externally adjusted scopes' rear mounts moved .0002" per 1/4th moa click and their 7.2 inch base spacing moved the scope 1/4 inch per hundred yards. Such is life when their adjustment screws have 40 threads per inch and the detent ring makes their spring loaded ball cllick 50 times per revolution. .025 inch per thread divided by 50 equals .0002 inch per click.</p><p></p><p>And metallic aperture sights were made with their adjustment lead screws had 40 threads per inch. One turn of the knob with a standard 30 inch sight radius moved the aperture .025 inch and one third of that's .008333 inch which is 1/3600th of the sight radius so 1/3600th of 100 yards is exactly one inch.</p><p></p><p>The above aside, some scopes are not quite exactly 4 clicks per inch at 100 yards because the thread pitch and spacing between the erector tube's pivot point and the adjustment flats aren't such to be exactly on. Measure the click value by clampng your scope in a vise then seeing how far the reticule moves for 40 clicks on a target at 100 yards. If it's anything but exactly 10 inches on the target, note what the error is.</p><p></p><p>Forget the trigonometric value that puts 1 moa of trig equalling about 1.0472 inch.</p></blockquote><p></p>
[QUOTE="Bart B, post: 568252, member: 5302"] In the shooting sports here in the USA, they're both the same. That came to be long ago when both smallbore and highpower target rings were spaced in even inches apart. That was established over a hundred years ago when externally adjusted scopes' rear mounts moved .0002" per 1/4th moa click and their 7.2 inch base spacing moved the scope 1/4 inch per hundred yards. Such is life when their adjustment screws have 40 threads per inch and the detent ring makes their spring loaded ball cllick 50 times per revolution. .025 inch per thread divided by 50 equals .0002 inch per click. And metallic aperture sights were made with their adjustment lead screws had 40 threads per inch. One turn of the knob with a standard 30 inch sight radius moved the aperture .025 inch and one third of that's .008333 inch which is 1/3600th of the sight radius so 1/3600th of 100 yards is exactly one inch. The above aside, some scopes are not quite exactly 4 clicks per inch at 100 yards because the thread pitch and spacing between the erector tube's pivot point and the adjustment flats aren't such to be exactly on. Measure the click value by clampng your scope in a vise then seeing how far the reticule moves for 40 clicks on a target at 100 yards. If it's anything but exactly 10 inches on the target, note what the error is. Forget the trigonometric value that puts 1 moa of trig equalling about 1.0472 inch. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Need help understanding why my ballistics calculator is doing this!!
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