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Cosine indicator question
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<blockquote data-quote="mattj" data-source="post: 210980" data-attributes="member: 8758"><p>I've seen an exercise like this before, but just for fun, plugged some numbers into Loadbase and did some math.</p><p></p><p></p><p>===========================================================</p><p>Roughly approximating a .300 RUM: BC .711 (240gr SMK), MV 2900fps ---</p><p></p><p>1000 yard level shot = 25.2 MOA drop</p><p></p><p>For shot at 20 degree angle:</p><p></p><p>Rifleman method: 1000 yards * cos(20) = 940 yards; Drop for level shot @ 940 yards = 22.9 MOA drop</p><p></p><p>Improved Rifleman method: 25.2 MOA * cos(20) = 23.7 MOA drop</p><p></p><p>Entering 20 shooting incline @ 1000 yards directly into LoadBase = 23.5 MOA drop</p><p></p><p></p><p>"Error" of Rifleman method vs. LoadBase direct incline entry = 2.6% (~6" @ 1000 yards)</p><p></p><p>"Error" of Improved Rifleman method vs. LoadBase direct incline entry = .9% (~2" @ 1000 yards)</p><p>===========================================================</p><p></p><p>Of course, the 240gr SMK is a nice slippery bullet, and the projectile is still going almost 1700 fps @ 1000. </p><p></p><p></p><p>The RUM is pretty forgiving at "only" 1000 yards though... let's try a .308 Win:</p><p></p><p></p><p>===========================================================</p><p>Roughly approximating a .308 Win: BC .505 (175gr SMK), MV 2700fps ---</p><p></p><p>1000 yard level shot = 37.1 MOA drop</p><p></p><p>For shot at 20 degree angle:</p><p></p><p>Rifleman method: 1000 yards * cos(20) = 940 yards; Drop for level shot @ 940 yards = 33.1 MOA drop</p><p></p><p>Improved Rifleman method: 37.1 MOA * cos(20) = 34.9 MOA drop</p><p></p><p>Entering 20 shooting incline @ 1000 yards directly into LoadBase = 34.6 MOA drop</p><p></p><p>"Error" of Rifleman method vs. LoadBase direct incline entry = 4.5% (~15" @ 1000 yards)</p><p></p><p>"Error" of Improved Rifleman method vs. LoadBase direct incline entry = .9% (~3" @ 1000 yards)</p><p>===========================================================</p><p></p><p>I'll leave the conclusion drawing to the individual reader, 'cause I'm tired <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /></p></blockquote><p></p>
[QUOTE="mattj, post: 210980, member: 8758"] I've seen an exercise like this before, but just for fun, plugged some numbers into Loadbase and did some math. =========================================================== Roughly approximating a .300 RUM: BC .711 (240gr SMK), MV 2900fps --- 1000 yard level shot = 25.2 MOA drop For shot at 20 degree angle: Rifleman method: 1000 yards * cos(20) = 940 yards; Drop for level shot @ 940 yards = 22.9 MOA drop Improved Rifleman method: 25.2 MOA * cos(20) = 23.7 MOA drop Entering 20 shooting incline @ 1000 yards directly into LoadBase = 23.5 MOA drop "Error" of Rifleman method vs. LoadBase direct incline entry = 2.6% (~6" @ 1000 yards) "Error" of Improved Rifleman method vs. LoadBase direct incline entry = .9% (~2" @ 1000 yards) =========================================================== Of course, the 240gr SMK is a nice slippery bullet, and the projectile is still going almost 1700 fps @ 1000. The RUM is pretty forgiving at "only" 1000 yards though... let's try a .308 Win: =========================================================== Roughly approximating a .308 Win: BC .505 (175gr SMK), MV 2700fps --- 1000 yard level shot = 37.1 MOA drop For shot at 20 degree angle: Rifleman method: 1000 yards * cos(20) = 940 yards; Drop for level shot @ 940 yards = 33.1 MOA drop Improved Rifleman method: 37.1 MOA * cos(20) = 34.9 MOA drop Entering 20 shooting incline @ 1000 yards directly into LoadBase = 34.6 MOA drop "Error" of Rifleman method vs. LoadBase direct incline entry = 4.5% (~15" @ 1000 yards) "Error" of Improved Rifleman method vs. LoadBase direct incline entry = .9% (~3" @ 1000 yards) =========================================================== I'll leave the conclusion drawing to the individual reader, 'cause I'm tired :) [/QUOTE]
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