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Rifles, Reloading, Optics, Equipment
Long Range Scopes and Other Optics
Ranging game with mil dots
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<blockquote data-quote="sscoyote" data-source="post: 162935" data-attributes="member: 1133"><p>Good question Len. This is where reverse "milling" helps to understand the error that can be expected from the system. OK, suppose u're using the TMR reticle that has super-fine ranging stadia at .2 mil (.72 IPHY). You're hunting antelope in WY, and u've snuck up to the edge of a shallow basin, and there the big 1 stands way out there (assume 15" back to brisket for a buck according to the Kahles website). Now at 500 yds. he would bracket 4.2 subtension units--</p><p></p><p>15 x 100 / .72 / X = 500</p><p>X= 4.2</p><p></p><p>Now suppose u're +/- .1 subtension units off with that reticle. Here's the range of error--</p><p></p><p>4.1 = 508 yds.</p><p></p><p>4.3 = 484 yds.</p><p></p><p>miss or hit?? Depends on the cartridge assuming a 10" vital zone (pg. 105 of Bob Hagel's "...Game Loads and Practical ballistic for the Amer. Hunter--great book, BTW, IMO). Of course u're aiming dead center on his chest, so that means +/- 5".</p><p></p><p>OK, now he's +/- 1" chest depth measurement @ 4.2 subtension units--</p><p></p><p>14 x 100 / .72 / 4.2 = 463 yds.</p><p>16 x 100 / .72 / 4.2 = 530 yds.</p><p></p><p>...so???</p><p></p><p>700 YDS. = </p><p></p><p>15 x 100 / .72 / X = 700</p><p></p><p>X = 3.0 SU's</p><p></p><p>15 x 100 / .72 / 2.9 = 718</p><p>15 x 100 / .72 / 3.1 = 672</p><p></p><p>14 x 100 / .72 / 3.0 = 648</p><p>16 x 100 / .72 / 3.0 =741</p><p></p><p>...so???</p><p></p><p>It's my opinion that any subtension unit has an interpolative accuracy of .1 of it's total subtension--</p><p></p><p>TMR = .1 x .72 IPHY = .072 IPHY accuracy</p><p>MD = .1 x 3.6 IPHY = .36 IPHY accuracy</p><p></p><p>This is why i like the finer stadia, as it does help somewhat.</p><p></p><p>Now, how important that is for big game depends on the individual to make that decision--for a coyote or chuck tho., at least for me i don't really care. I'll hurl 1 his way.</p></blockquote><p></p>
[QUOTE="sscoyote, post: 162935, member: 1133"] Good question Len. This is where reverse "milling" helps to understand the error that can be expected from the system. OK, suppose u're using the TMR reticle that has super-fine ranging stadia at .2 mil (.72 IPHY). You're hunting antelope in WY, and u've snuck up to the edge of a shallow basin, and there the big 1 stands way out there (assume 15" back to brisket for a buck according to the Kahles website). Now at 500 yds. he would bracket 4.2 subtension units-- 15 x 100 / .72 / X = 500 X= 4.2 Now suppose u're +/- .1 subtension units off with that reticle. Here's the range of error-- 4.1 = 508 yds. 4.3 = 484 yds. miss or hit?? Depends on the cartridge assuming a 10" vital zone (pg. 105 of Bob Hagel's "...Game Loads and Practical ballistic for the Amer. Hunter--great book, BTW, IMO). Of course u're aiming dead center on his chest, so that means +/- 5". OK, now he's +/- 1" chest depth measurement @ 4.2 subtension units-- 14 x 100 / .72 / 4.2 = 463 yds. 16 x 100 / .72 / 4.2 = 530 yds. ...so??? 700 YDS. = 15 x 100 / .72 / X = 700 X = 3.0 SU's 15 x 100 / .72 / 2.9 = 718 15 x 100 / .72 / 3.1 = 672 14 x 100 / .72 / 3.0 = 648 16 x 100 / .72 / 3.0 =741 ...so??? It's my opinion that any subtension unit has an interpolative accuracy of .1 of it's total subtension-- TMR = .1 x .72 IPHY = .072 IPHY accuracy MD = .1 x 3.6 IPHY = .36 IPHY accuracy This is why i like the finer stadia, as it does help somewhat. Now, how important that is for big game depends on the individual to make that decision--for a coyote or chuck tho., at least for me i don't really care. I'll hurl 1 his way. [/QUOTE]
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