Re: IMPORTANT REQUEST
Here’s the come ups for both riflesight combinations from 100yard zeros. Sierra’s 1996 software was used and it’s proved very, very accurate getting come ups from my own 100yard 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 10degree 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 20degree 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 (20inch then 24inch barrels), then by ranges starting at 200 yards and every 100 yards out to 1000. Each range will have a 20degree temperature band with the come up. Here’s an example for comeups from a 100 yard zero to 500 yards for the 24inch barrel:
“800 yd: 85105F=28.7 moa, 106125F=26.1 moa, 126145F=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 20inch barrel, sight height 2.5 inches, M118 with 173gr. M2 bullet leaving at 2500 fps
At 25 yards, impact is 1.3 inches low for a 100yard zero
Come ups from 100yard zero
200 yds; 85105F=1.9 moa, 106125F=1.9 moa, 126145F=1.9 moa
300 yds; 85105F=5.0 moa, 106125F=5.0 moa, 126145F=4.9 moa
400 yds; 85105F=8.6 moa, 106125F=8.5 moa, 126145F=8.3 moa
500 yds; 85105F=12.7 moa, 106125F=12.6 moa, 126145F=12.2 moa
600 yds; 85105F=17.4 moa, 106125F=17.1 moa, 126145F=16.5 moa
700 yds; 85105F=22.5 moa, 106125F=22.1 moa, 126145F=21.3 moa
800 yds; 85105F=28.4 moa, 106125F=27.7 moa, 126145F=26.5 moa
900 yds; 85105F=34.9 moa, 106125F=33.9 moa, 126145F=32.3 moa
1000 yds; 85105F=42.2 moa, 106125F=40.9 moa, 126145F=38.6 moa
M24 with 24inch barrel, sight height 1.5 inches, M118 with 173gr. M2 bullet leaving at 2600 fps
At 25 yards, impact is 0.6 inch low for a 100yard zero
Come ups from 100yard zero
200 yds; 85105F=2.2 moa, 106125F=2.1 moa, 126145F=2.1 moa
300 yds; 85105F=5.1 moa, 106125F=5.1 moa, 126145F=5.0 moa
400 yds; 85105F=8.5 moa, 106125F=8.5 moa, 126145F=8.3 moa
500 yds; 85105F=12.4 moa, 106125F=12.2 moa, 126145F=11.9 moa
600 yds; 85105F=16.6 moa, 106125F=16.4 moa, 126145F=15.9 moa
700 yds; 85105F=21.4 moa, 106125F=21.0 moa, 126145F=20.2 moa
800 yds; 85105F=26.7 moa, 106125F=26.1 moa, 126145F=25.0 moa
900 yds; 85105F=32.6 moa, 106125F=31.8 moa, 126145F=30.3 moa
1000 yds; 85105F=39.3 moa, 106125F=38.2 moa, 126145F=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 threequarter value wind)
Wind from 2, 4, 8, and 10 o’clock; 87% of full value (or a seveneigths value wind)
Let me know how these numbers work out.
