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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
bullet drop and scope leveling
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<blockquote data-quote="Bart B" data-source="post: 103051" data-attributes="member: 5302"><p>[ QUOTE ]</p><p>This may sound wierd, but the rotation of the earth will cause the bullet to drift to the right, in our hemisphere.</p><p>What say you all? </p><p></p><p>[/ QUOTE ]</p><p>Having worn out several barrels shooting long range competition in all directions using both aperture and scope sights with the same zero for all ranges through 1000 yards, I can attest to the fact that the coriolis effect of the earth spinning at different speeds (about 500 yards per second at the equator) depending on latitude is zero. If there was an effect, I and all the other master class long range competitors would use a different windage zero for each range. No correction is needed; our windage zero didn't change for range. Most of the time aperture sights were used. The front sight has a spirit level that was zeroed with the elevation axis of the rear sight. After zeroing at 100 yards in a zero wind condition then coming up in elevation what's needed to zero at 1000 yards, windage didn't change. Same thing with scopes.</p><p></p><p>Large caliber long range military projectiles do need a correction. The gun aiming computers I worked on aboard Navy ships had an input for latitude that ended up making corrections to gun orders to correct for the coriolis earth rotating effect. Corrections at ranges less than 2000 yards were negligible. As range increased to 45,000 yards the correction got bigger. Corrections were made up to 70 degrees of latitude; above that the trig functions got too cumbersome to make mechanical computing cams for.</p><p></p><p>This guy probably has a canted scope reticule which can easily be corrected.</p></blockquote><p></p>
[QUOTE="Bart B, post: 103051, member: 5302"] [ QUOTE ] This may sound wierd, but the rotation of the earth will cause the bullet to drift to the right, in our hemisphere. What say you all? [/ QUOTE ] Having worn out several barrels shooting long range competition in all directions using both aperture and scope sights with the same zero for all ranges through 1000 yards, I can attest to the fact that the coriolis effect of the earth spinning at different speeds (about 500 yards per second at the equator) depending on latitude is zero. If there was an effect, I and all the other master class long range competitors would use a different windage zero for each range. No correction is needed; our windage zero didn’t change for range. Most of the time aperture sights were used. The front sight has a spirit level that was zeroed with the elevation axis of the rear sight. After zeroing at 100 yards in a zero wind condition then coming up in elevation what’s needed to zero at 1000 yards, windage didn’t change. Same thing with scopes. Large caliber long range military projectiles do need a correction. The gun aiming computers I worked on aboard Navy ships had an input for latitude that ended up making corrections to gun orders to correct for the coriolis earth rotating effect. Corrections at ranges less than 2000 yards were negligible. As range increased to 45,000 yards the correction got bigger. Corrections were made up to 70 degrees of latitude; above that the trig functions got too cumbersome to make mechanical computing cams for. This guy probably has a canted scope reticule which can easily be corrected. [/QUOTE]
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bullet drop and scope leveling
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