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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Up/Downhill corrections
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<blockquote data-quote="Shawn Carlock" data-source="post: 156618" data-attributes="member: 4"><p>Here is a sample I shot to confirm all of this: 1276 yards, downhill .90, 3630 ft., 62 degrees, 55% etc., I have shot with my 338 Edge (of course). If you look at standard flatline drop for 1275 yards you need 33.50 moa. If you correct the yardage with the cosine to get 1148 yards and get dope for that distance you need 28.50 moa. If you apply the .90 cosine to the dope for 1275 yards you get 30.00 moa. The exbal program gives you 32.00 moa even. When I shot this I needed 31.75 moa. The applyed cosine methods will result in a low miss of 26" and 47" at this distance. So as you can see any method other than using the PC will make you shoot low at this angle and distance with this caliber. The printed Exbal angle chart like the one above is what I now use for a backup to the PC. I still need the ACI but apply it to the PC. Applying the cosine to anything else is not as accurate and on some distances &amp; angles it can be quite a difference.</p><p></p><p>Let generate one more example take the 308 Win 175 gr SMK match round. 800 yards, 45 degrees (.71 cos), 0', 78%, 29.53 bar, 59 deg temp.</p><p></p><p>Flatline dope for 800 yds 26.50 moa</p><p>800 x .71 = 568 yds dope for 568 15.75 moa</p><p>Dope for 800, 26.50 x .71 = 18.75 moa</p><p>Exbal generation 17.50 moa</p><p></p><p> This is more of the original post the cosine applied to the distance always generates low dope, cosine applied to dope for the yardage can give both high and low dope depending on distance angle and the round being used. Like I said above out to a certain distance depending on caliber any of the methods will work for hunting / field shooting, but after a certain point you have to use the PC or Exbal generated sheet to be accurate enough to make good solid first round hits. The simple fact is that while applying cosine to drop or distance will get hits out to a distance it is not the most accurate way to do it and I just wanted everyone to be aware of the margin of error in the other methods. If you don't shoot past 600 yards this info may mean nothing to your hunting performance.</p></blockquote><p></p>
[QUOTE="Shawn Carlock, post: 156618, member: 4"] Here is a sample I shot to confirm all of this: 1276 yards, downhill .90, 3630 ft., 62 degrees, 55% etc., I have shot with my 338 Edge (of course). If you look at standard flatline drop for 1275 yards you need 33.50 moa. If you correct the yardage with the cosine to get 1148 yards and get dope for that distance you need 28.50 moa. If you apply the .90 cosine to the dope for 1275 yards you get 30.00 moa. The exbal program gives you 32.00 moa even. When I shot this I needed 31.75 moa. The applyed cosine methods will result in a low miss of 26" and 47" at this distance. So as you can see any method other than using the PC will make you shoot low at this angle and distance with this caliber. The printed Exbal angle chart like the one above is what I now use for a backup to the PC. I still need the ACI but apply it to the PC. Applying the cosine to anything else is not as accurate and on some distances & angles it can be quite a difference. Let generate one more example take the 308 Win 175 gr SMK match round. 800 yards, 45 degrees (.71 cos), 0', 78%, 29.53 bar, 59 deg temp. Flatline dope for 800 yds 26.50 moa 800 x .71 = 568 yds dope for 568 15.75 moa Dope for 800, 26.50 x .71 = 18.75 moa Exbal generation 17.50 moa This is more of the original post the cosine applied to the distance always generates low dope, cosine applied to dope for the yardage can give both high and low dope depending on distance angle and the round being used. Like I said above out to a certain distance depending on caliber any of the methods will work for hunting / field shooting, but after a certain point you have to use the PC or Exbal generated sheet to be accurate enough to make good solid first round hits. The simple fact is that while applying cosine to drop or distance will get hits out to a distance it is not the most accurate way to do it and I just wanted everyone to be aware of the margin of error in the other methods. If you don't shoot past 600 yards this info may mean nothing to your hunting performance. [/QUOTE]
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