Range Report A question about Ballistic FTE wind calculations

[ReaperDriver]

The latest Ballistic FTE ver 3.2.4 for the iphone has several wind entries that I'm unsure how to use correctly. Under "atmospheric conditions", it has a field with Wind position with 3 choices of Muzzle, midrange, downrange. For example, if I know what the wind is at all three positions (by taking readings with a handheld kestrel), which is the prefered position? Muzzle gives me the most deflection of the three if I use the same value. Or would it be better to average it somehow and use the midrange position?

Also, there is a "upwind velocity" input field. If I put in any value other than 0, it changes the mil drop value rather than the windage deflection. For instance at 1000 yds, my default drop is 12.18 mils. If I add in 10 mph for the upwind velocity" field - the windage stays the same but now the drop is 9.24 mils. that's a big change. What is upwind velocity doing for me and how do I use it?

 

[ChadTRG42]

Re: A question about Ballistic FTE wind calculations

Muzzle wind is most important. You can use the mid range and target wind for your really long shots. If you had different cross winds mid range, then you can enter it, but I just use the muzzle figures. Your target wind is going to be your least important, since the bullet is already there.
An example of an up wind is if you are shoot across a canyon and the wind is vertical, or something similar. I've never used an upwind calculation.

 

[GrimmRoper]

Re: A question about Ballistic FTE wind calculations

+1 on Muzzle wind.

consider your shooting like a story book. You dont need to worry about the ending "target wind" or the middle of the book "midrange wind" before you start the book.

The muzzle is where you will see the greatest amount of deflection and therefore you need to deal with it first.

-Nate

 

[Lindy]

Re: A question about Ballistic FTE wind calculations

I recommend that readers interested in this subject get a copy of Bryan Litz's book, Applied Ballistics for Long Range Shooting.

We tend to pay more attention to the wind at the shooter's position, because we can know it more precisely.

The wind does not act on the bullet the way many think it does, by blowing the bullet sideways. The bullet actually weathervanes into the relative wind created by a crosswind.

In addition, as the bullet goes downrange, it's slowing down, and the crosswind has more time to act on the bullet.

Bryan's book on this subject is worth reading.

 

[ReaperDriver]

Re: A question about Ballistic FTE wind calculations

So does Ballistic FTE allow me to enter all three winds or do I have to choose one of the three positions?

 

[ReaperDriver]

Re: A question about Ballistic FTE wind calculations

Bump. No one else with Ballistic FTE experience or info? Anyone?

 

[gugubica]

Re: A question about Ballistic FTE wind calculations

Reaper, you have to choose one.

 

[TimK]

Re: A question about Ballistic FTE wind calculations

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gugubica</div><div class="ubbcode-body">Reaper, you have to choose one. </div></div>

Yup, you have to pick one. It'd be nice if they'd allow simultaneous different values since the wind isn't even always blowing the same direction, let alone the same velocity.

 

[ReaperDriver]

Re: A question about Ballistic FTE wind calculations

ok, got it. Thanks. I used only "Muzzle" wind today and it got me very close out to 1K. Swirling and changing winds do suck though :-(

 

[onetoe]

Re: A question about Ballistic FTE wind calculations

I read in another post where Lindy had recommended Applied Ballistics for Long Range Shooting. Being fairly new to this particular sport I purchased the book and it was extremly helpful. As always I pick up good information off the hide.

Thanks

Bradley

 

[CCCP2k]

Re: A question about Ballistic FTE wind calculations

This whole business with muzzle, midrange and downrange wind in FTE confuses hell out of me.

This how they explain it on their WEB site:

Wind Position: The position at which the strongest wind is crossing; by default, this is set to "Muzzle", but can also be set to "Midrange" or "Downrange". Ballistic will adjust your windage (and elevation, if an upwind is specified) based on where the wind is strongest.

What the hell? What do they mean by it? What wind speeds they use in each setting at each part of the range? Let's say I pick "Midrange". Are muzzle and downrange parts considered blocked or have some other wind speed? I do not see how this thing may work. It does not have parameters required to perform calculations.

I think only Muzzle can be used with constant wind that covers all range or as a base for more complicated cases. After that it's your guess based on experience. You may add or subtract some drift according to what you see over range distance.

Wind reading is not exact science, it's art

Here is a book you may want to read:

"The Wind Book for Rifle Shooters" by Linda K. Miller and Keith Cunningham. I have seen Keith in action and was really impressed. People say that Linda is even better in it.

It will not answer all the questions but it's an excellent start.

 

[CoryT]

Re: A question about Ballistic FTE wind calculations

If that's the new approach, you'll need to make an average wind call across the shot range and then use Muzzle. It's a app, what did you expect?

 

[CCCP2k]

Re: A question about Ballistic FTE wind calculations

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CoryT</div><div class="ubbcode-body">If that's the new approach, you'll need to make an average wind call across the shot range and then use Muzzle. It's a app, what did you expect? </div></div>

You are right, the only problem the average may not work for all cases. You may also have to factor somehow the readings you call if they significantly different and cover different parts of the range. E.g. at 1000 meters 5 m/s (0-600) and 1 m/s (600-1000). Apparently 5 m/s muzzle wind will have more effect than average 3 from 0-600. Will average 3 compensate the error down the range? It is hard to tell. I would say it should underestimate the drift. We apply smaller wind at muzzle for 600 meters and bigger wind the rest of the distance which is shorter (400 meters). Muzzle wind is more important but we reduced it's importance by averaging.
In this case 4 may be a better call.

The problem could be easily solved by providing wind values at different distances. You could use Muzzle wind most of the times but also have an ability to add one or even 2 values if you can read them down the range.