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Long Range Competition
Rotational projectile drift
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<blockquote data-quote="BallisticsGuy" data-source="post: 1327815" data-attributes="member: 96226"><p>^^^ That's a really smart way of dealing with it. You're at 2-3 clicks of spin at 1000 (according to my math) and substantially short of that it's hard for 2-3 clicks to be of too much consequence. For most shooters just the slop in wind call nets more horizontal error than that. </p><p></p><p></p><p></p><p>FWIW, I get 6.8" (.82MOA) using my formula for a stereotypical 6.5CM load. This is not saying anything about your data other than, it looks like whatever system you're using and mine are outputting very comparable results, meaning the model is highly effective. </p><p></p><p>On my .223 running 75gn Hornady HPBT on a 9 twist I get 1 full MOA of spin at 1000yrds (about 11 inches). At 700yrds it's just 2 clicks for .48MOA which is only a bit over 3". At 500yrds it's 1 click meaning about 1.5 inches. On my new 7 twist barrel it's not much more, about 1 more click at 1000yrds and really nothing additional under that. This is because the real mover and shaker for spin drift is time of flight as the math of the matter raises ToF to the power of 1.83, nearly squaring the value. Because the adjustments are angular you also need the target to be really far away for the very small angles at play to mean much in the grand scheme of things.</p></blockquote><p></p>
[QUOTE="BallisticsGuy, post: 1327815, member: 96226"] ^^^ That's a really smart way of dealing with it. You're at 2-3 clicks of spin at 1000 (according to my math) and substantially short of that it's hard for 2-3 clicks to be of too much consequence. For most shooters just the slop in wind call nets more horizontal error than that. FWIW, I get 6.8" (.82MOA) using my formula for a stereotypical 6.5CM load. This is not saying anything about your data other than, it looks like whatever system you're using and mine are outputting very comparable results, meaning the model is highly effective. On my .223 running 75gn Hornady HPBT on a 9 twist I get 1 full MOA of spin at 1000yrds (about 11 inches). At 700yrds it's just 2 clicks for .48MOA which is only a bit over 3". At 500yrds it's 1 click meaning about 1.5 inches. On my new 7 twist barrel it's not much more, about 1 more click at 1000yrds and really nothing additional under that. This is because the real mover and shaker for spin drift is time of flight as the math of the matter raises ToF to the power of 1.83, nearly squaring the value. Because the adjustments are angular you also need the target to be really far away for the very small angles at play to mean much in the grand scheme of things. [/QUOTE]
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Rotational projectile drift
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