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Spreadsheet to determine best long range hunting cartridge
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<blockquote data-quote="Hand Skills" data-source="post: 1557963" data-attributes="member: 103303"><p>I'm with you</p><p></p><p></p><p>I'm pretty skeptical of 'killing power' metrics. As you handily pointed out, in the realm of expanding bullets which deform (change shape) on impact, sectional density is essentially meaningless.</p><p></p><p>I do however believe KPS is more representative than kinetic energy alone.</p><p>_____________________________</p><p></p><p></p><p><strong>THE MOST IMPORTANT IMPLICATION: <em>The larger diameter and/or heavier the bullet, the less downrange energy it needs to achieve a given KPS value</em></strong></p><p></p><p>Realizing this implication of the killing power formula was a <em>Eureka!</em>moment. Understanding this implication quickly led me to conclude that I could use it to quantitatively compare the downrange performance of different sizes and weights of bullets, driven at different velocities.</p><p></p><p>The key to such comparisons is specifying a KPS value of interest. Suppose I wish to determine the energy level at which three different sizes and weights of hunting bullets would have a KPS value of 15.</p><p></p><p>I start by rearranging the KPS formula to read: <strong>E = KPS / (SD x F)</strong>. Dividing the KPS value, 15, by the (SD x A) product of each of the three bullets specified below tells me the energy level at which each would generate a KPS of 15.</p><p></p><ul> <li data-xf-list-type="ul">.243 dia., 100 gr. (SD .242, A .0464) - Energy for KPS of 15 = 1337 ft. lbs.</li> <li data-xf-list-type="ul">.277 dia., 130 gr. (SD .242, A .0603) - Energy for KPS of 15 = 1029 ft. lbs.</li> <li data-xf-list-type="ul">.308 dia., 150 gr. (SD .226, A .0745) - Energy for KPS of 15 = 891 ft. lbs.</li> </ul><p>I can now determine and compare the ranges at which cartridges in these calibers and bullet weights get KPS values of 15. I will use Federal factory loads in .243 Winchester, .270 Winchester and .30-30 Winchester to illustrate. (The .243 and .270 loads use JSP spitzer bullets and the .30-30 load uses a RN bullet. MV values are for 24 inch barrels.</p><p></p><p>I used an online ballistics program to build a trajectory table for each load. I read down the energy column of the table to find the energy value that is closest to the target energy value I calculated above; then I read the yardage at which this energy value occurs.</p><p></p><p>Here are the results for the three loads: .243 Win., 100 gr. bullet = 195 yards; .270 Win., 130 gr. bullet = 510 yards (!); .30-30 Win., 150 gr. bullet = 215 yards.</p><p>________________</p><p></p><p>Source: <a href="https://www.chuckhawks.com/g-s_formula_implications.html" target="_blank">https://www.chuckhawks.com/g-s_formula_implications.html</a></p></blockquote><p></p>
[QUOTE="Hand Skills, post: 1557963, member: 103303"] I'm with you I'm pretty skeptical of 'killing power' metrics. As you handily pointed out, in the realm of expanding bullets which deform (change shape) on impact, sectional density is essentially meaningless. I do however believe KPS is more representative than kinetic energy alone. _____________________________ [B]THE MOST IMPORTANT IMPLICATION: [I]The larger diameter and/or heavier the bullet, the less downrange energy it needs to achieve a given KPS value[/I][/B] Realizing this implication of the killing power formula was a [I]Eureka![/I]moment. Understanding this implication quickly led me to conclude that I could use it to quantitatively compare the downrange performance of different sizes and weights of bullets, driven at different velocities. The key to such comparisons is specifying a KPS value of interest. Suppose I wish to determine the energy level at which three different sizes and weights of hunting bullets would have a KPS value of 15. I start by rearranging the KPS formula to read: [B]E = KPS / (SD x F)[/B]. Dividing the KPS value, 15, by the (SD x A) product of each of the three bullets specified below tells me the energy level at which each would generate a KPS of 15. [LIST] [*].243 dia., 100 gr. (SD .242, A .0464) - Energy for KPS of 15 = 1337 ft. lbs. [*].277 dia., 130 gr. (SD .242, A .0603) - Energy for KPS of 15 = 1029 ft. lbs. [*].308 dia., 150 gr. (SD .226, A .0745) - Energy for KPS of 15 = 891 ft. lbs. [/LIST] I can now determine and compare the ranges at which cartridges in these calibers and bullet weights get KPS values of 15. I will use Federal factory loads in .243 Winchester, .270 Winchester and .30-30 Winchester to illustrate. (The .243 and .270 loads use JSP spitzer bullets and the .30-30 load uses a RN bullet. MV values are for 24 inch barrels. I used an online ballistics program to build a trajectory table for each load. I read down the energy column of the table to find the energy value that is closest to the target energy value I calculated above; then I read the yardage at which this energy value occurs. Here are the results for the three loads: .243 Win., 100 gr. bullet = 195 yards; .270 Win., 130 gr. bullet = 510 yards (!); .30-30 Win., 150 gr. bullet = 215 yards. ________________ Source: [URL]https://www.chuckhawks.com/g-s_formula_implications.html[/URL] [/QUOTE]
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