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Elevation and ballistics
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<blockquote data-quote="Brent" data-source="post: 7543" data-attributes="member: 99"><p>Just looking at this chart I had been comparing altitudes on, a small MV reduction of 30 fps would mean an additional drop of 2.5" at 700yds and 5" at 1000yds.</p><p></p><p>A 50 fps reduction in MV would mean almost 4" at 700yds and 9" at 1000yds. </p><p></p><p></p><p>Some more food for thought:</p><p></p><p>Looking at reductions in MV and how well they compensate for a lower BP at 7000 ft. using standard conditions at altitude, with the round shooting 9" flatter at 700yds and 32" at 1000yds as refered to in my example before this; </p><p></p><p>If the MV was reduced by 165 fps by a temp sensitive powder being used, at 700 yds the bullet would be about 4" high and at 1000yds it would be zero, or right on POA.</p><p></p><p>If the MV was reduced by only 120 fps, the bullet would be zero at 700yds and still 21" high at 1000 yards though.</p><p></p><p>Point is, a slower MV will not change the change the trajectory curve in the same way air density will. A change in BC from the change in air density flattens the curve, dropping the MV steepens the trajectory curve and one will never balance the other out throught the whole curve. </p><p></p><p>If using a temp insensitive powder already, you could make charts using a higher BC bullet in Florida to simulate the lower drag you'll be shooting in at altitude, but you're probably shooting a pretty high BC bullet already.</p><p></p><p>If you were planning on hunting with a 178gr A-Max for instance with a .5 BC, that BC adjusted for 7000 ft. ASL would require a .610 BC to shoot at sea level in Florida to get drops for real close charts to use on the hunt.</p></blockquote><p></p>
[QUOTE="Brent, post: 7543, member: 99"] Just looking at this chart I had been comparing altitudes on, a small MV reduction of 30 fps would mean an additional drop of 2.5" at 700yds and 5" at 1000yds. A 50 fps reduction in MV would mean almost 4" at 700yds and 9" at 1000yds. Some more food for thought: Looking at reductions in MV and how well they compensate for a lower BP at 7000 ft. using standard conditions at altitude, with the round shooting 9" flatter at 700yds and 32" at 1000yds as refered to in my example before this; If the MV was reduced by 165 fps by a temp sensitive powder being used, at 700 yds the bullet would be about 4" high and at 1000yds it would be zero, or right on POA. If the MV was reduced by only 120 fps, the bullet would be zero at 700yds and still 21" high at 1000 yards though. Point is, a slower MV will not change the change the trajectory curve in the same way air density will. A change in BC from the change in air density flattens the curve, dropping the MV steepens the trajectory curve and one will never balance the other out throught the whole curve. If using a temp insensitive powder already, you could make charts using a higher BC bullet in Florida to simulate the lower drag you'll be shooting in at altitude, but you're probably shooting a pretty high BC bullet already. If you were planning on hunting with a 178gr A-Max for instance with a .5 BC, that BC adjusted for 7000 ft. ASL would require a .610 BC to shoot at sea level in Florida to get drops for real close charts to use on the hunt. [/QUOTE]
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