17 mph wind hold?

[fishwater]

I am looking for a little input here please.

I was shooting the other day and encountered something weird.

A little background info: I am shooting 300 GR. OTM's out of a .338 LMAI that I got on here 2nd hand. I have had the gun 3 months and it has always shot very good. I have shot just over 120 rounds through it so far. I have a NF ATACR, and the scope is mounted totally straight. I have a Holland's level bubble, and I have tested it at 100 yards by dialing up 40 MOA and the bullet hits directly over a 100 yard zero shot, (OK maybe it's off by 1/4 inch or so... good enough for me... LOL.) Anyways, the point is that the scope is properly mounted and I do not cant the rifle when I shoot.

The shot...

Yesterday I was shooting at a 14" gong at 1220 yards. The shot was -4 deg downhill. The wind was coming in steady straight from the left at about 4 mph according to my Kestrel 2500. (The forecast for that day was a 10 mph wind.) I entered all my data into shooter, and it came back with a 30.6 MOA elevation hold, and a 3.0 MOA left windage correction. I shot once and nobody saw anything... Hmmm...

Shot again, and we saw an impact, I was perfect height, but I was around 6 MOA right! So I dialed in another 6 1/2 MOA and was on target. I proceeded to hit the 14" gong 3 times and even a milk jug at 1220 yards with that solution.

What I am wondering is: In order for me to get the shooter app to tell me the proper 9.5 MOA windage hold for that day, (121.7 inches, or about 10 feet.) I needed to tell it that there was a 17 mph left to right wind!

I was shooting across a VERY wide open canyon, and the wind was coming in right off a lake, right up the valley. But where I was it was only 4 mph. Elevation was around 2000 feet.

Now, I am a novice long range shooter, but this seems a little weird to me..

Any ideas on what may have been happening that day? Or is it normal for the wind to be highly concentrated coming through a canyon like that? 17 mph seems a little high to me.

Thanks.

 

[steeltraps]

When shooting valley to valley wind eddies and thermals can have a great effect on bullet flight. Just because you can see the wind or measure it up close does not mean its not doing something different at mid range. The wind that you CANT see is often the reason that our programs seam way off. You may often get strange winds from valleys. I have shot before at rocks In North Alabama and the wind AT my position be 2 mph and the wind at 1600 yards , not even be moving ANY leaves on the trees but the wind in between causes me to me WAY off. Like 3 moa at 1600 yards. Hope this helps

 

[bigngreen]

The wind is what keeps it interesting Look at the area your shooting as if water was flowing, look for terrain that will compress and speed up the air or when your taking a wind reading look to see if your set up in a super nice shooing location out of the wind
Each canyon has it's own temperament, take notes, find other areas to take a wind reading to help fill in your knowledge of that shot and each time you'll bring it in more till it pays of.

 

[fishwater]

I forgot to add in the first post that I was, and do enable and dial for Coriolis and spin drift every shot also...

So you guys think this is normal for shooting up in the hills?

I have never encountered this much wind drift before so I'm a little blown away..

Get it?? Blown away... LOL.

 

[cowboy]

It is more than likely that the wind is the culprit.

One of the things a lot of people forget is that we measure the wind with our meters no more than 6 ft off the ground and usually are watching grass and vegetation farther out to verify. Figure out how much elevation your bullet needs to reach that distance and there in lies the problem usually. Watch the wind on a high flag pole or building some time and make an educated guess to the mph, then take a wind reading at its base and with practice you can get better at it.

 

[bigngreen]

I have one spot we shoot that the target is in one draw and were shooting from two draws over through couple saddles for 1890 yards, the spot we shoot from is in kind of in a wind shadow so if we and we'll read a few mph their, walk out a couple hundred yards and you'll catch a 8 or 9 mph reading, get into the center of the saddle and stand on the truck roof and you'll catch a 22 mph. It's a fun and challenging to get a cold bore hit in that spot!!!

 

[royinidaho]

What bigngreen said…..

I think it was Broz who told me that Shawn says a stream flows faster in the middle that along the shores. Same with canyons and wind.

I have a spot that a multiplication factor of 1.2 works perfectly across a canyon from 600 to 1200 yards under any wind condition but zero. And there's never been a zero wind condition in Idaho in any canyon I've been in.

 

[steeltraps]

You guys are 100% right. Mide range wind will SOMETIMES drive a man crazy. Here is a good example. I use to have a least=lost it got out bid by another group. of 2000 acres. Had a 1400 yards range . We shot mountain top to mountaintop. Alabama foot hills really. 1600 ft to 1720ft . I would set at the bench and 4500 kestel would not move. I would look at the 1400 yards mansize steel targets and a 30 inch circle. Between and beside them were 4ft peices of orange flagging tape. They would be absolutlt still in the mornings. But some mornings I would have to put 5 moa of wind on it! That equals 6 mph wind? I read an have see a 5mph wind move a 3ft peice of flagging strait out at 5mph. Why was my flagging showing zero wind?? One day i could stand it now more. I Took and ranged a tree at midrange with my Vector 4. It was 802 yards a little past half way, where our rode went up the mountain. I took my friend and his ranger and a treestand the next day. Climbed up a big tree almost 60 ft, and hung flagging on treestand bow holders on both sides. The next day we where amaize at how thr almost half way flags were moving! They would be almost strait and the ones at the target up the hill 600 yards would be hanging down with only a slight flicker to indictat that they were even moving. But threw that valley WAS like a river of air !!

 

[fishwater]

Lots of good comments so far, thanks!

 

[FearNoWind]

Wind doping is a lifetime study that you never master. The variables are endless and the best you will ever do is understand how it (theoretically) effects your bullet - but you'll never fully understand where the effect takes place and at to what degree of influence over any given path at any given time.
Another factor is your scope adjustment accuracy. Can you be absolutely certain that 1 MOA of adjustment in the turret equals exactly 1 MOA at 1200 yards? Even the better grade scopes can have some degree of error in their range of adjustment.
Spend a few bucks and buy yourself a copy of "Applied Ballistics for Long Range Shooting" (Bryan Litz). His section on wind, all by itself, it worth the price of the book.
There's so much information in that book that I'll probably have to read my copy half a dozen times to get it all in my head but he backs his work up with solid scientific data so it's worth the time - besides winter is coming and I can read it again a couple of times before spring. gun)

 

[steeltraps]

Applied Ballistics For Long -Range Shooting = Second Edition is a great book! It also has a free ballistics program. The CD disk is great on a small labtop for those place you can get phone reseption to work your apps! Its very accurate too!gun)