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<blockquote data-quote="Bart B" data-source="post: 101345" data-attributes="member: 5302"><p>Roy, here's another way to get those "magic numbers" or range constants.</p><p></p><p>Let's take a 30 caliber 180-gr. spitzer boattail leaving at 2960 fps at an altitude of 6000 feet. At each range below, the wind drift in inches is for a 10 mph cross wind from 3 o'clock.</p><p></p><p>At 400 yards, 8.3 inches, 2.1 MOA correction needed</p><p></p><p>At 800 yards, 36.9 inches, 4.6 MOA correction needed</p><p></p><p>At 1200 yards, 94.1 inches, 7.8 MOA correction needed</p><p></p><p>What's needed is some number to divide the base formula's answer (Range in hundreds by Wind in mph) by to get the correction for a full value wind.</p><p></p><p>At 400 yards, 4 x 10 = 40, so 40 / 2.1 MOA = 19, the magic number (or constant) for this load at 400 yards.</p><p></p><p>At 800 yards, 8 x 10 = 80, so 80 / 4.6 MOA = 17, the magic number (or constant) for this load at 800 yards.</p><p></p><p>At 1200 yards, 12 x 10 = 120, so 120 / 7.8 MOA = 15, the magic number (or constant) for this load at 1200 yards.</p><p></p><p>Run the wind calculation formula for each range and see what MOA value you come up with for each one. Again, the formula is Range (in hundreds of yards) times Wind (in mph) divided by the Magic number. Or: RxW/M</p></blockquote><p></p>
[QUOTE="Bart B, post: 101345, member: 5302"] Roy, here’s another way to get those “magic numbers” or range constants. Let’s take a 30 caliber 180-gr. spitzer boattail leaving at 2960 fps at an altitude of 6000 feet. At each range below, the wind drift in inches is for a 10 mph cross wind from 3 o’clock. At 400 yards, 8.3 inches, 2.1 MOA correction needed At 800 yards, 36.9 inches, 4.6 MOA correction needed At 1200 yards, 94.1 inches, 7.8 MOA correction needed What’s needed is some number to divide the base formula’s answer (Range in hundreds by Wind in mph) by to get the correction for a full value wind. At 400 yards, 4 x 10 = 40, so 40 / 2.1 MOA = 19, the magic number (or constant) for this load at 400 yards. At 800 yards, 8 x 10 = 80, so 80 / 4.6 MOA = 17, the magic number (or constant) for this load at 800 yards. At 1200 yards, 12 x 10 = 120, so 120 / 7.8 MOA = 15, the magic number (or constant) for this load at 1200 yards. Run the wind calculation formula for each range and see what MOA value you come up with for each one. Again, the formula is Range (in hundreds of yards) times Wind (in mph) divided by the Magic number. Or: RxW/M [/QUOTE]
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