Taming the Wind
From Fred:
Fred's recent Worland, WY experience suggests he should be reading what he writes - from the "Starting Out" series, which is worth repeating here:
Use "hold-offs" when you have to fire a shot in a hurry and have to compensate for range or wind. Generally, you aim off no more than half a target. You aim...left or right edge on the upwind side, to allow for wind. (On a rare occasion, you may have to aim a full target off for wind, but you'll know in advance, because it'll be a windy day to start with. A 15 mph wind - a pretty stiff breeze from 3 or 9 o'clock - a full value wind - will blow you off the target 3 moa at 300, and 4 moa at 500. How many inches would that be at each distance, and how far off the center of the target would you have to aim to compensate?
Answer: 9 and 20, and half-a-target and a whole target, respectively.
Your M1A front sight is a help, as it is close to 7 moa wide -- the standard, not the narrow 'match' sight. If you were to put the downwind edge of the front sight COT, in effect you move the bullet 3 1/2 moa in the upwind direction. If you were to put the downwind edge of the sight on the upwind edge of the target at 500 yards, you'd move the bullet 5.5 moa upwind.
But remember: the sight moa does not change with distance; the 20-inch target size, expressed in moa, does change. So from COT to edge of target is 2 moa (10") at 500, but approximately 3 moa (9") at 300 yards; the 3.5 moa from center to edge of your 7 moa-wide sight remains the same at all distances.
You have determined how many moa YOUR front sight covers, right?
If not, it's really easy. Just take a target of known dimension, convert the target dimension to moa, post the target at 100 yards, and see how much of your known-dimension target is covered by your front sight.
Wanna make it even easier? Take two standard pieces of copier paper, 8.5" x 11". Post one sheet sideways at 100 yards, and place a bold black line at the halfway point of the target. Post the other sheet of paper lengthwise, also placing the bold black line at the halfway point. You now have an 11 moa/5.5 moa scale, as well as as 8.5/4.25 moa scale against which to compare your front sight. Note how much of the scale your front sight covers, mark that info down somewhere where you'll remember it, and you're good to go.
Now, being weekend warriors, it's hard to remember all the data on wind.
First, you have to know the effect of a wind of X MPH on your target at Y distance. Simplify by picking 300 and 500 yards.
Then determine direction - winds from 2-4 and 8-10 o'clock are "full value", whereas winds from 1, 5, 7, and 11 o'clock are "half-value", meaning you halve the adjustment you make. Winds from 12 and 6 you ignore. See what I mean by complicated?
How much you delve into this depends on anticipated conditions. If you live in a windy area - flat, open spaces, little vegetation - you may want to put a wind chart to refer to under the flipup next to your sight settings. Something like:
[Full Value] 10 mph 15 mph 20 mph
300 2 moa 3 moa 4 moa
500 3 moa 4 moa 6 moa
Full Value: winds from 2, 3, 4, 8, 9 & 10 o'clock
Half value: winds from 1, 5, 7 & 11 o'clock
[Fred NEEDED this chart at Worland! Cut it out and tape to your stock, so it'll be there when YOU need it.]
Now, just how strong IS that wind? Estimation of wind strength is hardly a science. 10 mph raises dust, and blows paper. 15 mph gets small trees swaying.
An almost universal wind correction at 500 for a full value wind is putting the downwind edge of the front sight on COT, moving bullet strike 3.5 moa upwind.
If you overestimated the wind - say it's only 10 mph, you¹ve moved the bullet impact 1/2 moa (2.5") too much, hardly enough to matter. If you underestimated the wind, and it's really 20 mph, you should've moved the downwind edge of the sight onto the upwind edge of the target, moving the bullet 5.5 moa upwind. So if you underestimate, you're 2.5 moa short, and that's enough to move you 12.5" off COT, good for a close miss on the downwind side.
But a 20 mph wind is a strong wind, one you'll recognize as a strong wind, and hopefully if a full value wind, at 500 you'll do the edge-to-edge thing, keeping your bullet on the target. One definite plus to the stronger winds: at the target, the wind noise could mask the report of your rifle, or, if heard, will cause it to "drift" in the downwind direction, making it harder for them to ID your location.
If, like Fred in WY, you get tossed into unfamiliar shooting in a strong wind, don't get flustered (easier said than done, Fred knows). It's like getting lost; don't lose self-control; stay calm.
Some modification: a fairly constant wind, adjust your sights so you aim dead on. Then hold off only when the wind picks up or slows down.
Tip #2: if you have the time, be patient. Wind surges and wanes; wait for the wind to lessen to fire your shot.
Wind: For the rifleman, it has more impact on hit probability than any other factor -since he already knows how to fire a good shot, his range estimation is decent, and the target is usually more sensitive to horizontal than vertical errors.
Your best bet? Take any opportunity you can get -- especially you folks in the East, who are a bit short on long-distance range availability -- to go and out shoot your rifle, with your standard load, at long and windy distances. There's no substitute for the experience and confidence that comes from busting rocks at 600+ yards with a stiff wind hitting you from 3 o'clock.
Man, we really needed this yesterday in Jericho and I couldn't find Fred's Simplified Wind Rule anywhere in the Guide, google, this forum or the old forum on my phone. I knew the gist of it from hearing it at a langhorne appleseed and the WW2 Garand training video, but not well enough give it as a point of instruction to people who really could have made use of it yesterday. Thanks to Riflesniper for chiming in with some help on it, but we really need to get it down cold including .223 and .308 effects.
I knew most of the wind rules off the top of my head, and drew a total blank on drift values for .223, 30-06 and 7.62 NATO. I should've been able to answer it, but, I just couldn't remember that part for some reason.
Folks the No value, half value. full value portion is easy, and very basic, but the MOA allowances for the given wind speeds is a whole different critter.
And crak, he's ripersnifle.
Quote from: Nickle on October 22, 2007, 06:31:12 PM
And crak, he's ripersnifle.
You know, I knew that and that's what my brain typed anyway.
Kinda like a joke about a toin coss (instead of a coin toss) from 2nd grade ruined those words for me for life. ???
An Instructor's handout for Appleseeds referencing the wind, and another referencing common elevation settings (not just M1/M14) will be coming soon.
Got on a good site to explain wind effect. First off, chrony your loads, whether reloads or factory loads, next know your drift at 100 yds for 1-3-5 and 10mph winds. You can calculate this at (JBM-calculations-trajectory).
You have to feed in info to this calculation being bullet design- coefficient- velocity and your zero range.Once you have this drift established for the 100 yd. range it becomes simply. Suppose you have 1" drift at 100yds irregardless of the wind, at 200yds you'll have 4", at 300 you'll have approx 9" drift. Now to explain: You take the 100yd increment, say 400yds would be 4, square it would be 16. That would be your drift at 400yds. with a 1" drift at 100yds. Remember these are not exact but close enough to get you on a 700yd. target. Square the 100yd. increment times the 100yd. drift =your drift at a designated distance. Suppose you have a range finder and read a 375yd shot. You know the drift at the current wind is .5" at 100 yds. Simply multiply 3.75x3.75x.5 and you have your drift for 375 yds. Another way is to print out a drift cheat book from this site aforementioned and add the drifts for the winds encountered. IE: you add the calculated drift effect of different speed winds, based on your JBM calcalations and you will have your answer. ONE MUST remember that cross winds of 10 mph do not have the same effect as a 10mph wind coming at you at a different angle other than 90 degrees. This will also have a formula that will correlate with the cross wind calculations as a percentage. All the training in the world done at 100-200 yards is near worthless when wind becomes your enemy. At 100-200 yards, most wind is of little or no consequence unless your are match shooting, however, at 500-700+ yds you better have your ducks in order on windy days or you'll waste a lot of ammo. Study it, understand it then practice it. A little history, in 1975 at Oceana Naval Base Rifle Range I fired a 238 out of 250 with a M1A while incountering a double cross wind. One at near the 300 and a reverse wind at the 500. Had it not been for those guys running the range knowing how to read these winds and helping us with the proper wind corrections this score would never have been possible. I thanked them for thier knowledge. Latter.