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Extreme Long Range Hunting & Shooting (ELR)
How do you judge wind
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<blockquote data-quote="stormc" data-source="post: 2997216" data-attributes="member: 39048"><p>I've found that wind at the beginning of a projectile's path has a greater effect at long range than the same wind at the end of its path.</p><p>Let's say your target is at 1760 yards. Your bullet has a G7 BC of .442 @ 3100 fps. </p><p>You have a strong cross wind from the left for the first 400 yards. This wind has enough to energy to accelerate your bullet to 2 fps away from your line of site, to the right, in that first 400 yards. From 400 yards on the wind is dead calm, but your bullet is still on a 2 fps tangent to the right, away from your line of sight.</p><p>It's going to take it about 2.3 seconds to reach the target. Now, we can't multiply 2 fps x the full 2.3 seconds because it took the first 400 yards to accelerate your bullet to 2 fps away from your line of sight. So let's round it down to about 4 feet.</p><p></p><p>So now let's say the wind changes, and it's dead calm to 1360 yards, with that same strong cross wind from the left for the LAST 400 yards.</p><p>It's going to take your bullet about .65 seconds to travel that last 400 yards, about one quarter of a second longer than it did the first 400, so it will accelerate to more than 2 fps away from your line of sight, let's say 2.5 fps. We can't multiply 2.5 fps x the full .65 seconds (1'-71/2") because the bullet had to accelerate from dead on to 2.5 fps in 400 yards, so let's round it down to 14".</p><p>Sorry about the redneck math!</p></blockquote><p></p>
[QUOTE="stormc, post: 2997216, member: 39048"] I’ve found that wind at the beginning of a projectile’s path has a greater effect at long range than the same wind at the end of its path. Let’s say your target is at 1760 yards. Your bullet has a G7 BC of .442 @ 3100 fps. You have a strong cross wind from the left for the first 400 yards. This wind has enough to energy to accelerate your bullet to 2 fps away from your line of site, to the right, in that first 400 yards. From 400 yards on the wind is dead calm, but your bullet is still on a 2 fps tangent to the right, away from your line of sight. It’s going to take it about 2.3 seconds to reach the target. Now, we can’t multiply 2 fps x the full 2.3 seconds because it took the first 400 yards to accelerate your bullet to 2 fps away from your line of sight. So let’s round it down to about 4 feet. So now let’s say the wind changes, and it’s dead calm to 1360 yards, with that same strong cross wind from the left for the LAST 400 yards. It’s going to take your bullet about .65 seconds to travel that last 400 yards, about one quarter of a second longer than it did the first 400, so it will accelerate to more than 2 fps away from your line of sight, let’s say 2.5 fps. We can’t multiply 2.5 fps x the full .65 seconds (1’-71/2”) because the bullet had to accelerate from dead on to 2.5 fps in 400 yards, so let’s round it down to 14”. Sorry about the redneck math! [/QUOTE]
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