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<blockquote data-quote="Bart B" data-source="post: 105396" data-attributes="member: 5302"><p>Here's the come ups for both rifle-sight combinations from 100-yard zeros. Sierra's 1996 software was used and it's proved very, very accurate getting come ups from my own 100-yard zeros in four .308 Win. rifles using their 155, 168, 180, 190 and 200 gr. 30 caliber match bullets. But only when accurate muzzle velocity data is known. With variables such as bore, groove and chamber dimensions, these will effect a given round's muzzle velocity. And then you add powder temperature at firing (heated from spending a while in a hot barrel or storage/carrying place, more changes to muzzle velocity will happen. And the difference in air temperature for each 10-degree F change even at 1000 yards is only 6/10ths MOA at most. As there's probably going to be enough actual muzzle velocity than the numbers I used to make that much difference, I'm going to use three 20-degree temperature bands. But this data is at least a starting point. It would be interesting to see how it compares to others provided.</p><p></p><p>The info below is grouped by each rifle (20-inch then 24-inch barrels), then by ranges starting at 200 yards and every 100 yards out to 1000. Each range will have a 20-degree temperature band with the come up. Here's an example for come-ups from a 100 yard zero to 500 yards for the 24-inch barrel:</p><p></p><p> "800 yd: 85-105F=28.7 moa, 106-125F=26.1 moa, 126-145F=25.0 moa</p><p></p><p>If the range is 800 yards and the temperature is 109 degrees F, come up 26 MOA from the 100 yard zero. You'll hit within 4 inches vertically if your actual muzzle velocity is 2600 fps.</p><p></p><p>Heres the numbers:</p><p></p><p>SR25 with 20-inch barrel, sight height 2.5 inches, M118 with 173-gr. M2 bullet leaving at 2500 fps</p><p>At 25 yards, impact is 1.3 inches low for a 100-yard zero</p><p>Come ups from 100-yard zero</p><p>200 yds; 85-105F=1.9 moa, 106-125F=1.9 moa, 126-145F=1.9 moa</p><p>300 yds; 85-105F=5.0 moa, 106-125F=5.0 moa, 126-145F=4.9 moa</p><p>400 yds; 85-105F=8.6 moa, 106-125F=8.5 moa, 126-145F=8.3 moa</p><p>500 yds; 85-105F=12.7 moa, 106-125F=12.6 moa, 126-145F=12.2 moa</p><p>600 yds; 85-105F=17.4 moa, 106-125F=17.1 moa, 126-145F=16.5 moa</p><p>700 yds; 85-105F=22.5 moa, 106-125F=22.1 moa, 126-145F=21.3 moa</p><p>800 yds; 85-105F=28.4 moa, 106-125F=27.7 moa, 126-145F=26.5 moa</p><p>900 yds; 85-105F=34.9 moa, 106-125F=33.9 moa, 126-145F=32.3 moa</p><p>1000 yds; 85-105F=42.2 moa, 106-125F=40.9 moa, 126-145F=38.6 moa</p><p></p><p>M24 with 24-inch barrel, sight height 1.5 inches, M118 with 173-gr. M2 bullet leaving at 2600 fps</p><p>At 25 yards, impact is 0.6 inch low for a 100-yard zero</p><p>Come ups from 100-yard zero</p><p>200 yds; 85-105F=2.2 moa, 106-125F=2.1 moa, 126-145F=2.1 moa</p><p>300 yds; 85-105F=5.1 moa, 106-125F=5.1 moa, 126-145F=5.0 moa</p><p>400 yds; 85-105F=8.5 moa, 106-125F=8.5 moa, 126-145F=8.3 moa</p><p>500 yds; 85-105F=12.4 moa, 106-125F=12.2 moa, 126-145F=11.9 moa</p><p>600 yds; 85-105F=16.6 moa, 106-125F=16.4 moa, 126-145F=15.9 moa</p><p>700 yds; 85-105F=21.4 moa, 106-125F=21.0 moa, 126-145F=20.2 moa</p><p>800 yds; 85-105F=26.7 moa, 106-125F=26.1 moa, 126-145F=25.0 moa</p><p>900 yds; 85-105F=32.6 moa, 106-125F=31.8 moa, 126-145F=30.3 moa</p><p>1000 yds; 85-105F=39.3 moa, 106-125F=38.2 moa, 126-145F=36.1 moa</p><p></p><p>Here's wind correction data using the old military formula Range (in hundreds of yards) times Wind speed (in mph) divided by the range constant for the MOA correction for a full value wind from 3 or 9 o'clock. For other wind angles, take a fraction of the answer. Example: at 900 yards with a 13 mph wind from 1 o'clock, 9 times 13 is 117, then dividing 117 by the 900 yard constant of 11 equals almost 8, and a 1 o'clock wind is worth 50% of full value, so you would put on 4 minutes of right wind correction and would be within a couple of inches of what's exact for Sierra's calculations.</p><p></p><p>100 and 200 yards, constant is 15</p><p>300 and 400 yards, constant is 14</p><p>500 and 600 yards, constant is 13</p><p>700 and 800 yards, constant is 12</p><p>900 and 1000 yards, constant is 11</p><p></p><p>Wind from 12:30, 5:30, 6:30 and 11:30 o'clock, 25% of full value (or quarter value wind)</p><p>Wind from 1, 5, 7, and 11 o'clock; 50% of full value (or half value wind)</p><p>Wind from 1:30, 4:30, 7:30 and 10:30 o'clock, 75% of full value (or three-quarter value wind)</p><p>Wind from 2, 4, 8, and 10 o'clock; 87% of full value (or a seven-eigths value wind)</p><p></p><p>Let me know how these numbers work out.</p></blockquote><p></p>
[QUOTE="Bart B, post: 105396, member: 5302"] Here’s the come ups for both rifle-sight combinations from 100-yard zeros. Sierra’s 1996 software was used and it’s proved very, very accurate getting come ups from my own 100-yard zeros in four .308 Win. rifles using their 155, 168, 180, 190 and 200 gr. 30 caliber match bullets. But only when accurate muzzle velocity data is known. With variables such as bore, groove and chamber dimensions, these will effect a given round’s muzzle velocity. And then you add powder temperature at firing (heated from spending a while in a hot barrel or storage/carrying place, more changes to muzzle velocity will happen. And the difference in air temperature for each 10-degree F change even at 1000 yards is only 6/10ths MOA at most. As there’s probably going to be enough actual muzzle velocity than the numbers I used to make that much difference, I’m going to use three 20-degree temperature bands. But this data is at least a starting point. It would be interesting to see how it compares to others provided. The info below is grouped by each rifle (20-inch then 24-inch barrels), then by ranges starting at 200 yards and every 100 yards out to 1000. Each range will have a 20-degree temperature band with the come up. Here’s an example for come-ups from a 100 yard zero to 500 yards for the 24-inch barrel: “800 yd: 85-105F=28.7 moa, 106-125F=26.1 moa, 126-145F=25.0 moa If the range is 800 yards and the temperature is 109 degrees F, come up 26 MOA from the 100 yard zero. You’ll hit within 4 inches vertically if your actual muzzle velocity is 2600 fps. Heres the numbers: SR25 with 20-inch barrel, sight height 2.5 inches, M118 with 173-gr. M2 bullet leaving at 2500 fps At 25 yards, impact is 1.3 inches low for a 100-yard zero Come ups from 100-yard zero 200 yds; 85-105F=1.9 moa, 106-125F=1.9 moa, 126-145F=1.9 moa 300 yds; 85-105F=5.0 moa, 106-125F=5.0 moa, 126-145F=4.9 moa 400 yds; 85-105F=8.6 moa, 106-125F=8.5 moa, 126-145F=8.3 moa 500 yds; 85-105F=12.7 moa, 106-125F=12.6 moa, 126-145F=12.2 moa 600 yds; 85-105F=17.4 moa, 106-125F=17.1 moa, 126-145F=16.5 moa 700 yds; 85-105F=22.5 moa, 106-125F=22.1 moa, 126-145F=21.3 moa 800 yds; 85-105F=28.4 moa, 106-125F=27.7 moa, 126-145F=26.5 moa 900 yds; 85-105F=34.9 moa, 106-125F=33.9 moa, 126-145F=32.3 moa 1000 yds; 85-105F=42.2 moa, 106-125F=40.9 moa, 126-145F=38.6 moa M24 with 24-inch barrel, sight height 1.5 inches, M118 with 173-gr. M2 bullet leaving at 2600 fps At 25 yards, impact is 0.6 inch low for a 100-yard zero Come ups from 100-yard zero 200 yds; 85-105F=2.2 moa, 106-125F=2.1 moa, 126-145F=2.1 moa 300 yds; 85-105F=5.1 moa, 106-125F=5.1 moa, 126-145F=5.0 moa 400 yds; 85-105F=8.5 moa, 106-125F=8.5 moa, 126-145F=8.3 moa 500 yds; 85-105F=12.4 moa, 106-125F=12.2 moa, 126-145F=11.9 moa 600 yds; 85-105F=16.6 moa, 106-125F=16.4 moa, 126-145F=15.9 moa 700 yds; 85-105F=21.4 moa, 106-125F=21.0 moa, 126-145F=20.2 moa 800 yds; 85-105F=26.7 moa, 106-125F=26.1 moa, 126-145F=25.0 moa 900 yds; 85-105F=32.6 moa, 106-125F=31.8 moa, 126-145F=30.3 moa 1000 yds; 85-105F=39.3 moa, 106-125F=38.2 moa, 126-145F=36.1 moa Here’s wind correction data using the old military formula Range (in hundreds of yards) times Wind speed (in mph) divided by the range constant for the MOA correction for a full value wind from 3 or 9 o’clock. For other wind angles, take a fraction of the answer. Example: at 900 yards with a 13 mph wind from 1 o’clock, 9 times 13 is 117, then dividing 117 by the 900 yard constant of 11 equals almost 8, and a 1 o’clock wind is worth 50% of full value, so you would put on 4 minutes of right wind correction and would be within a couple of inches of what’s exact for Sierra’s calculations. 100 and 200 yards, constant is 15 300 and 400 yards, constant is 14 500 and 600 yards, constant is 13 700 and 800 yards, constant is 12 900 and 1000 yards, constant is 11 Wind from 12:30, 5:30, 6:30 and 11:30 o’clock, 25% of full value (or quarter value wind) Wind from 1, 5, 7, and 11 o’clock; 50% of full value (or half value wind) Wind from 1:30, 4:30, 7:30 and 10:30 o’clock, 75% of full value (or three-quarter value wind) Wind from 2, 4, 8, and 10 o’clock; 87% of full value (or a seven-eigths value wind) Let me know how these numbers work out. [/QUOTE]
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