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Rifles, Reloading, Optics, Equipment
Reloading
Accuracy versus velocity
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<blockquote data-quote="LRNut" data-source="post: 1868086" data-attributes="member: 3230"><p>Actually, it is even worse at 1200 than 800 (funny, those are the two ranges I practice at least weekly). The .8 MOA load will group 9.6 inches, leaving .2 inches of allowable wind error. At 3000 fps, that Berger drifts 7.1 inches for every mile of wind. You would have to guess the wind perfectly; within three hundreds of a mile per hour.</p><p></p><p>The same bullet at 2800 but shooting .4 MOA would group 4.8 inches, leaving you 2.6 inches on either end. The bullet drifts slightly more (7.9 inches per one mile of wind) but your allowable error is .3 mph, 10 times that of the faster bullet.</p><p></p><p>Incidentally, probably not a popular thing to point out here, but TOF is 1.7 seconds, so assuming you can call the wind to within .3 mph, you need it not to vary by that much during the TOF (not going to happen) or you may not hit. So much for wounding...</p><p></p><p>Again, these numbers are for a 100 percent probability of a hit. You can be pretty sloppy with your wind call and still hit 50% of the time. </p><p></p><p>One final (maybe) observation: any shot in which you get feedback (a small gong, watching the bullet impact, looking in a spotting scope, etc) will cause you to naturally adjust and if you shoot enough in one sitting, you can delude yourself into thinking you are great at wind calls. For example, I used to take one shot at 800, then look where I hit, then shoot at 1200 (different angle, so the wind was different). Knowing where I hit at 800 was hugely beneficial. Yesterday I called the wind 2 MOA at 800 (Edge, 2820 w/ Berger 300s) - it was blowing pretty hard from behind to about 7 o'clock - a wind I hate, since the angle changes so fast and has a much larger impact than the same angle change but from 3 or 9 o'clock. I didn't see the impact, but swung around to shoot at 1200. Mirage was different, so I called the wind 5 mph vs the 6-7 (full value) call I had at 800. My SIG said 2.25 MOA. But I always check mirage using the side parallax on my NF scopes, and thought it had picked up, so I held 3 MOA L. Elevation was a few inches high but windage was 1.25 MOA left - a huge miss. But, at 800 I had a perfect wind call. If I had looked at the 800 yard shot, I would have held closer to 2 than 3 (because the 1200 yard rock is a 3/4 wind vs a 9 oclock wind at 800).</p></blockquote><p></p>
[QUOTE="LRNut, post: 1868086, member: 3230"] Actually, it is even worse at 1200 than 800 (funny, those are the two ranges I practice at least weekly). The .8 MOA load will group 9.6 inches, leaving .2 inches of allowable wind error. At 3000 fps, that Berger drifts 7.1 inches for every mile of wind. You would have to guess the wind perfectly; within three hundreds of a mile per hour. The same bullet at 2800 but shooting .4 MOA would group 4.8 inches, leaving you 2.6 inches on either end. The bullet drifts slightly more (7.9 inches per one mile of wind) but your allowable error is .3 mph, 10 times that of the faster bullet. Incidentally, probably not a popular thing to point out here, but TOF is 1.7 seconds, so assuming you can call the wind to within .3 mph, you need it not to vary by that much during the TOF (not going to happen) or you may not hit. So much for wounding... Again, these numbers are for a 100 percent probability of a hit. You can be pretty sloppy with your wind call and still hit 50% of the time. One final (maybe) observation: any shot in which you get feedback (a small gong, watching the bullet impact, looking in a spotting scope, etc) will cause you to naturally adjust and if you shoot enough in one sitting, you can delude yourself into thinking you are great at wind calls. For example, I used to take one shot at 800, then look where I hit, then shoot at 1200 (different angle, so the wind was different). Knowing where I hit at 800 was hugely beneficial. Yesterday I called the wind 2 MOA at 800 (Edge, 2820 w/ Berger 300s) - it was blowing pretty hard from behind to about 7 o'clock - a wind I hate, since the angle changes so fast and has a much larger impact than the same angle change but from 3 or 9 o'clock. I didn't see the impact, but swung around to shoot at 1200. Mirage was different, so I called the wind 5 mph vs the 6-7 (full value) call I had at 800. My SIG said 2.25 MOA. But I always check mirage using the side parallax on my NF scopes, and thought it had picked up, so I held 3 MOA L. Elevation was a few inches high but windage was 1.25 MOA left - a huge miss. But, at 800 I had a perfect wind call. If I had looked at the 800 yard shot, I would have held closer to 2 than 3 (because the 1200 yard rock is a 3/4 wind vs a 9 oclock wind at 800). [/QUOTE]
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