Near wind or far wind ?

[AlanF]

Thanks Dave. Great post. I'll see if Peter still has the simulator available.

[plumbs7]

Thanks for ur time and. Contribution . This what I was exactly hoping for when I started this post . A lot good advice 👍.

[DaveMc]

A few years ago I did some calculations on the 155 Sierra factory NRAA ammo. Here is the results assuming no elevation velocity difference for flight path -
First 100 yards 13 inches, 2nd 100 12.8, 3rd, 12.7, 4th 12.0, 5th 11.2, 6th 10.4, 7th 9.3, 8th 7.7, 9th 5.3 and final 100 = 1.9 inches (total 96 minutes)

When you start to add some increasing wind with elevation and realize the top of the flight path is 6-700 yards down range it soon becomes apparent that the first 7-8 hundred yards all flags are basically (rule of thumb) equal and only the last 100 or (200) it starts to really fall away.

Whether this is right or wrong I believe it is very close and the reason you have so much "conjecture" about near wind and far wind. Most are pretty equal - and certainly all have an effect.

So another rule of thumb I used for the 155 HBC at 3000fps was to allow 1 minute per 10mph (crosswind) for first 7 then the last few added together for another minute (or slightly more). Using Peters software this makes for interesting "games" when you set the flags to be opposing and certainly gets the mind thinking fast with practice.

I personally think you should train yourself to watch all flags if you can. If the flags are set correctly (and in bullet flight path) they all should show the relative wind in their section. You may have a funnel where the wind is at its highest (and changes the quickest) - this flag may be sitting on 16 mph and others at 4mph (or backwards) but they all tell an accumulative story down the range. Training yourself to do some quick mental arithmetic certainly helps get you closer to the centre. I take a look at all flags down the range whilst target is down. (occasionally things are in the right position where the line of flags are just upwind and with both eyes open you can get the full line of flags in the left eye superimposed over the scope image right up until shot is broken- this can be a magic situation for shooting and have had it in both Mackay and Brisbane). But regardless I do try and keep an eye on the "danger flags" or mirage up until the shot is pulled.

[Frank Green]

Graham,

It depends very much on the topography of the range, location of shelter trees, wind direction etc. But even for the simple situation of cross-wind on a flat range, it depends on who you listen to . James Owens in his book "READING THE WIND" says the closer flags are more important, whilst David Tubb looks at central or further flags!

Mr Owens theory is that because closer winds deflect the bullet sooner in its flight, then the overall effect will be greater. I haven't heard Mr Tubb's explanation.

Personally I subscribe to the Owens explanation, although with fluid dynamics, things are not always as they seem!

Alan

Alan, I think you got it right on the money. The geography of the range and surrounding area plays a huge part.

When Jim Ownes started having/teaching hi power rifle match classes back around 1990 or so I took like three of them real early on and I tend to agree with him that it's early in the bullet flight that it gets effected the most. I know Jim has shot around the world and shot on and coached the Marine Corp. rifle teams. So he has a lot of first hand experience to go off of.

Again though geography/range lay out plays a part. At the 2009 U.S. F-Class Championships at Lodi (range faces West) I had Tubb on my target one day and scored one of his relays. He thought from what I was seeing and hearing from him he had the range/conditions figured out. When I was watching thru my spotting scope I could not pick out what he thought he was seeing. Long story short he thought he seen the conditions come back and got on his gun and took his shot. He got a a wide 8 for score out of the shot. This happend to him a couple of times.

Also scoring for another shooter and this is the point of the story and again it was at a 1k yards. The shooter had a nice 10 and then a X for his two sighters. All of the range flags were hugging the poles and showed no real wind etc... When he went for his first record shot again all of the flags hugged the poles. Except for one of the two middle range flags. Those middle range flags are approx. 600 and 700 yards from the 1k yard line. One of the two middle flags picked up and showed a 15mph wind and pointed straight North. The shooter didn't catch it at all. Took his first shot for record and blew a round into the 7 ring out the right. I talked to him later and he said he never saw that flag until after the gun had gone off.

Lodi has some trees and open areas on the left side of the range. The right side of the range is mostly trees and berms etc...what I learned at that range is if those two middle flags don't agree you don't shoot. If you shoot you take your chances.

There is an old range/access road that comes in around the 500 yard line etc...the wind if coming from the South it can be coming in at one speed hit the North side of the range and go back out the South side at a different speed etc...guys try and read the mirage when that's happening and cannot figure out the mirage. This is because the nearer opening/flag is giving them a different reading than the other one is and I feel you get a false mirage etc....

Knowing the range your shooting at can give you a nice edge. If I don't know the range I will take my changes off of the closer flags etc....and if I'm not shooting first I will try and watch shooters that I know are good and try to see what they are doing etc...

Later, Frank

[Frank Green]

Some food for thought for ya.....just shot a mid range F-Class match (300, 500, 600 yards) yesterday. Wind was fairly consistent 90 degrees from the left (only a few let ups) and the wind was mostly 15-20mph but again the speeds seemed consistent. I was shooting on the small end of the line.

At 300 yards the flags pointed straight out and to the right. I basically had a 1/2moa of wind on my gun at 300 yards. From 300 yards to the targets the berm is shorter and the range isn't protected as much etc....

Moved back to 500 yards. You get some more protection from the berm I ended up running 3/8moa of wind on my gun. So I took 1/8 moa off.

Moved back to 600 yards and in the end was only running 1/8 moa total. Took another 1/4moa off the gun.

So with the conditions being pretty constant I will say that in this case....yes the bullet is effected more when it first leaves the gun.

I'm pretty sure I won the match. Will get final results later today. My scores where:

195-7x at 300 yards, 200-11x at 500 yards and a 197-10x at 600 yards.

Later, Frank