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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
A case for BDC Turrets
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<blockquote data-quote="Bart B" data-source="post: 509032" data-attributes="member: 5302"><p>Nope. It all had to do with the competition targets' scoring rings spaced at even inch diameters many long years ago.</p><p></p><p>A shooter's minute of angle was established over a century ago with Springfield 1903's 30 inch sight radius and micrometer rear sights moving .008333.... inch per minute or every 4 clicks on 40 tpi lead screws. That's 1/3600th of 30 inches; so is exactly one inch relative to 100 yards. All the Lyman, Vaver, Redfield, Gates, Clerke, Warner and other American made aperture sights were/are made this way. European aperture sights use a metric system that's different than MOA's.</p><p></p><p>Furthermore, when externally adjusted scopes were made popular, their adjutments moved exactly .002 inch with 4 clicks and with a 7.2 inch spacing on the mounts, that's also 1/3600ths of the spacing. So they too, moved 1/4 inch per click on the target. Such is life with Unertl, Remington, El Monte, Lyman, Sidle, Litchert and other externally adjusted scopes.</p><p></p><p>This is the shooting sports; not trig. There's four different meanings for a "mil" so 'tis no big deal to just learn what it is.</p><p></p><p>Col. Hatcher proved in the 1930's that a .30-06 M1 bullet only spin drifts about 3 inches at 1000 yards. And there's not enough coriolis to worry about. I doubt anybody can judge first shot wind drift to that accuracy.</p></blockquote><p></p>
[QUOTE="Bart B, post: 509032, member: 5302"] Nope. It all had to do with the competition targets' scoring rings spaced at even inch diameters many long years ago. A shooter's minute of angle was established over a century ago with Springfield 1903's 30 inch sight radius and micrometer rear sights moving .008333.... inch per minute or every 4 clicks on 40 tpi lead screws. That's 1/3600th of 30 inches; so is exactly one inch relative to 100 yards. All the Lyman, Vaver, Redfield, Gates, Clerke, Warner and other American made aperture sights were/are made this way. European aperture sights use a metric system that's different than MOA's. Furthermore, when externally adjusted scopes were made popular, their adjutments moved exactly .002 inch with 4 clicks and with a 7.2 inch spacing on the mounts, that's also 1/3600ths of the spacing. So they too, moved 1/4 inch per click on the target. Such is life with Unertl, Remington, El Monte, Lyman, Sidle, Litchert and other externally adjusted scopes. This is the shooting sports; not trig. There's four different meanings for a "mil" so 'tis no big deal to just learn what it is. Col. Hatcher proved in the 1930's that a .30-06 M1 bullet only spin drifts about 3 inches at 1000 yards. And there's not enough coriolis to worry about. I doubt anybody can judge first shot wind drift to that accuracy. [/QUOTE]
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A case for BDC Turrets
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