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Rifles, Reloading, Optics, Equipment
Reloading
SD's and ES's??????? Help!!
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<blockquote data-quote="SBruce" data-source="post: 428443" data-attributes="member: 21068"><p>It's ES or extreme spread that makes the difference. ES is the difference between the maximum velocity in a particular group of shots vs the minumum velocity in the same group of shots. Too much ES and you will get vetical stringing of your groups at long distance. Too much ES will also make the wind affect your shots differently at the same distance.</p><p> </p><p>Let's say you're shooting at 900 yds. you've got a 15 mph wind blowing from 04:30. and your loads have got an ES of 75 feet per second. (We'll assume you're shooting a 6 Long Dasher and a .48 BC bullet, cause I've got that loaded into my program)</p><p> </p><p>If you happen to shoot the extreme ends of your velocity for your first two shots (entirely possible) then the first one would impact over 8" different vertical and 2" different horizontal from the 2nd shot............just because the difference in the velocity of round 1 vs round 2. This is ONLY taking into account the delta V, not cold bore vs warm bore or normal variation in point of impact due to alot of different things.</p><p> </p><p>Now, lets take the same situation and use an ES of 20 feet per second. Your difference in point of impact for the same two shots would be only 2" vertical and 1/2" horizontal.</p><p> </p><p>SD or Standard Deviation is much harder to explain and calculate. It is basically a Statisticians argument and takes alot of shots over a <strong>very accurate</strong> chronograph to accurately determine. I wouldn't worry about it.</p><p> </p><p>If you only plan on shooting out to 700 yds, then the differences quoted above would be much much less. If your 1 moa groups at 700 yds are nice and round, and don't have more vertical than horizontal........you're ES's are probably ok.............just depends on how far you're gonna shoot and what size targets you plan on shooting at.</p><p> </p><p>Hope this answers your Q's.</p></blockquote><p></p>
[QUOTE="SBruce, post: 428443, member: 21068"] It's ES or extreme spread that makes the difference. ES is the difference between the maximum velocity in a particular group of shots vs the minumum velocity in the same group of shots. Too much ES and you will get vetical stringing of your groups at long distance. Too much ES will also make the wind affect your shots differently at the same distance. Let's say you're shooting at 900 yds. you've got a 15 mph wind blowing from 04:30. and your loads have got an ES of 75 feet per second. (We'll assume you're shooting a 6 Long Dasher and a .48 BC bullet, cause I've got that loaded into my program) If you happen to shoot the extreme ends of your velocity for your first two shots (entirely possible) then the first one would impact over 8" different vertical and 2" different horizontal from the 2nd shot............just because the difference in the velocity of round 1 vs round 2. This is ONLY taking into account the delta V, not cold bore vs warm bore or normal variation in point of impact due to alot of different things. Now, lets take the same situation and use an ES of 20 feet per second. Your difference in point of impact for the same two shots would be only 2" vertical and 1/2" horizontal. SD or Standard Deviation is much harder to explain and calculate. It is basically a Statisticians argument and takes alot of shots over a [B]very accurate[/B] chronograph to accurately determine. I wouldn't worry about it. If you only plan on shooting out to 700 yds, then the differences quoted above would be much much less. If your 1 moa groups at 700 yds are nice and round, and don't have more vertical than horizontal........you're ES's are probably ok.............just depends on how far you're gonna shoot and what size targets you plan on shooting at. Hope this answers your Q's. [/QUOTE]
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SD's and ES's??????? Help!!
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