Posted: 12/26/2016 5:59:42 PM EDT
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Hope this is the right forum.
Hunting Christmas morning I had one of those hunting show monsters step out. You know, the one that is about six years old with a rack with about a twenty six inside spread. Twelve point. It happened to me. The deer is as discribed. Stepped out at 319 yards measured by laser range finder. I have made the shot in lite to calm winds before on deer. Problem was a 35 mph cross wind blowing right to left at the target. The severe cross wind had me vexed so I passed up the shot because I would rather see him next year than wound him and not recover him. So the question of how much windage to use in a severe cross wind. Equipment used is a Browning x bolt, top with a Burris 3x9x42 scope. Ammo is Remington 150 grain coreloks. Barrel length is 22 inches. Sighted in 1.75 inches high at 100 yards. The rifle shoots 1/2 inch groups all day if th shooter does his part. I was just curious as to where to hold in this type of cross wind. Sorry, 30-06 caliber  
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Ok, 30-06 150gr PSP CoreLokt has a BC of .314, and MV rated is 2900, lets say yours is 2800 with a 22" barrel.
With a 35mph wind at full value for the entire distance, that is 35" of wind @ 300. By comparison - a 10mph wind is pushing it 10" @ 300. If you were wrong on the wind "guess".... each MPH at that distance and load is roughly an inch. So any more than 6-10 mph off and you are taking a big risk. |
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Another problem is even if you have a chart in hand and truly measure the wind or guess it correctly there is no guarantee the wind is constant for the whole distance.
In other words , with extreme conditions at longer distance it is really a crap shoot. I believe in this case holding off on the risky shot was the smart thing . Hope you get a shot on the big guy in the future in better conditions |
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With the information given, we have no way to guess.
But given calm conditions from gun to 1/2 distance and 10 MPH wind from 1/2 distance to target, figuring goes as follows:: calm from 0 to 160 yards:: windage on table is 1.0 MoA 10 MPH from 160 to 320 :: windage on table is 2.1 MoA but since 1.7 of that did not take place, the windage call becomes 2.1-1.0 = 1.1 MoA. Now, of course, I used the ballistics data from my loading, so you need to get the ballistics data on your loading. The math is the same--table lookup and subtract. |
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Using Hornady's ballistics calculator:
0 ft altitude 78% humidity temp 59* MV at 2900fps 90* wind angle of 35 mph and assuming wind speed is constant all the way to the target. BC (G1) of 0.2 for round nose 30 cal 150gr corelokts (I couldn't find the exact BC of this particular projectile ranging from 0.193 to 0.226). Wind drift: 300 yards: 60.9" 325 yards: 73.2" 350 yards: 87" |
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There's a easy formula that generally will get you in the ballpark for most standard horsepower 30 cal. cartridges (using middle of the road weight projectiles) within 800yds or so. I saw it in a magazine article so I can't take credit for it... I'm pretty sure it came from the owner of Black Hills Ammo in an interview he gave. It was called something like "Range minus 1". In other words...take the range in hundreds of yards (so for 300 yds you'd use 3)...then the "minus 1" part would be three minus one which would be 2. Now you multiply them together. 3x2=6. And that is your wind hold for a 10 mph direct crosswind... 6"
Give it a shot using a ballistic calculator and your information. It may work for you and it may not. If it does work for your rifle/load then when you have a quick shot and have to make a best guess...it will pay off. So, for 400 yds...that would be 4x3=12" windage hold off for a 10mph direct crosswind. Say the wind was 20mph, it would just be double that or 24". Say the wind wasn't a direct crosswind but only 70%, then you just apply that multiplier to your answer. For me, I use a 308 with 155gr bullets. Just off the top of my head using the "range minus 1" trick I'd guess for a 319yd shot with a 35mph direct crosswind that the windage hold would be: 3x2=~6" (doing some ballpark round offs and knowing that it would have really been 3.2x2.2 I'd guess more like 7 instead of 6). Then multiplying that answer of 7 by 3.5 (for a 35mph wind instead of 10mph) I'd get ~25" of windage hold. Real easy to do that quickly in your head without having to look at your phone app or any printed tables. Looking at my ballistic app on my phone the real answer for that situation would have been around 26.7". So...it works out for my rifle/load fairly well. |
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Quoted:
Using Hornady's ballistics calculator: 0 ft altitude 78% humidity temp 59* MV at 2900fps 90* wind angle of 35 mph and assuming wind speed is constant all the way to the target. BC (G1) of 0.2 for round nose 30 cal 150gr corelokts (I couldn't find the exact BC of this particular projectile ranging from 0.193 to 0.226). Wind drift: 300 yards: 60.9" 325 yards: 73.2" 350 yards: 87" The BC of that projectile is .314. Those numbers are way off. |
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This guy sounds like an expert.  Quoted:
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Zero your 30-06 3" high at 100 yards and dead on the deer in the middle And maybe 1" left or right depending on which direction of crosswind Don't need a formula for 300 yards This guy sounds like an expert. Highly probable it would be a kill shot also. 300 yards is not very far. Even in the wind. Folks generally over estimate wind drift. I came up with 7 moa of drift at 300y w/ 35 mph at a 90 degree. I highly doubt it was a true 35 mph at a 90. |
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Highly probable it would be a kill shot also. 300 yards is not very far. Even in the wind. Folks generally over estimate wind drift. I came up with 7 moa of drift at 300y w/ 35 mph at a 90 degree. I highly doubt it was a true 35 mph at a 90. Wind speed was at the airport which is about 8 miles as the crow flies and wind speed at ft. hood (about 25 miles away, fun to watch night gunnery practice) was between 20 and 30 with gusts to 40 that morning. Degrees was a guess but was blowing right to left. |
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The BC of that projectile is .314. Those numbers are way off. As stated, I was getting conflicting answers to actual BC. There seems to also be some variations in corelokt bullets, some round nose and pointed soft tips. Depending on which one you use would dictate BC. Using .314 as the BC with all other info being the same at 325 yards, it would be 41.7". |