Wind problem episode 277

[kriller134]

500 yards full value at 25 mph Plate is .6 wide
My rifle is a 5mph gun.
0.5x5=2.5 is my hold +/- 0.3
My bracket hold would be 2.2-2.8?
@lowlight am I missing anything?

 

[Lowlight]

That works,
5th bracket

 

[FrozenFingers]

Oh now I get it.

 

[Adkhunter3]

I think i get the math he did, just subbed .5 for .6 to make the math a little quicker. Where is the +/- .3 coming from? and where did you get 5th bracket from?

 

[Hawkguy29]

+/- .3 comes from the “wind budget” or room for error for the size plate if you hold center.

As far as the bracket goes for his gun (5mph gun) at 500m the first bracket is .5 for 5mph wind, 2nd bracket 1.0mil for 10mph, 3rd bracket 1.5mils 15mph wind, 4th-2.0mils for 20mph wind and finally 5th bracket will be 2.5mils for 25mph wind.

Correct me if I’m wrong here.

 

[Deleted member 113831]

I think i get the math he did, just subbed .5 for .6 to make the math a little quicker. Where is the +/- .3 coming from? and where did you get 5th bracket from?

No. The 0.5 comes from the range which is 500 yards.

The 5th bracket comes from a 5mph gun in a 25mph wind. 25/5=5.

The 0.3 comes from the target being 0.6 wide and therefore 0.3 from center to edge.

 

[Adkhunter3]

Thank you both ^ I got now.

 

[Shootnwrench]

Problem
.6mil target @ 500yds, 25mph wind

Solving for
.308 175smk = 4mph gun

25mph/4mph = 6.25
6.25 x .5 = 3.125 Or call it 3.1 Mil correction

Solving for
6.5C 140’s = 6mph gun

25mph/6mph = 4.166
4.166 x .5 = 2.08 or call it 2.1 Mil correction

 

[Leatherlunger]

These podcasts got me thinking it would be nice to have a wind budget chart on my “sheet” to understand my wiggle room for various sized targets at different yardages. I havent tried it out yet so well see how it goes next time im at the range. In theory you could use it to determine hit probability for max and min wind speeds. Again havent tried it out yet, see how it goes. Its the red column on the far right.

 

[Leatherlunger]

So looking at the chart in red at 700 yards. i could be off a little less than 2mph on a 9” target, a little less than 4mph on an 18” target and little less than 8mph on a 36” target for my wind read accuracy. Btw this is based on a 4 mph rifle at my home DA. In my dumb brain this would potentially get a touch on target as long as my verticle was good and my inital wind estimation was good. Again i think this is right based on listening to the podcast but we will see

 

[Leatherlunger]

Although thinking about it now should the error budget be the full width of a given target size or half of it?

 

[ma smith]

should wind budget begin with target size less inherenet error from weapons system?

ie 1 moa gun vs 2 moa target has MAX 1moa wind budget?

 

[Hawkguy29]

Although thinking about it now should the error budget be the full width of a given target size or half of it?

Well if you want a center hit then it would be half the size. However if you just want a hit, hold the upwind edge of plate and you have a few more mph of wind (budget) to play with. But the right answer is half the width for a center hit.

 

[Lowlight]

You really don't have time to play with error size,

You assume you can hit the target, so if you have a .5 plate and can put a .3 and .6 hold on it, you do that... and not worry about your miss, cause there is always potential to miss

 

[Leatherlunger]

Copy that Frank. I guess by playing with the error budget concept on a table, at least it gained me some perspective on probability for varying ranges if I misjudged the wind. Its been neat to learn about all this stuff thank you.

 

[MakeSawdust]

The simple math has been stated above. The full scenario for the day and determining where to hold may, or may not, involve more thought than that. With extremely limited time I would make a guess at the crosswind, given here as 25 mph. A 4 mph gun at 500 yds is 6*0.5=3 plus 1 mph at 500 yds is roughly .1 so hold 3.1 to center.

With more time to watch wind and understand the conditions we could potentially game the gusts. Gusts have patterns, typically. If we have enough time to figure out the pattern we can tell when the wind speed is increasing and when it is decreasing and get an idea of the highs and lows.

Let's you shoot in what you believe is the average of 25 mph and hold 3.1 and you get an edge hit at say 3.3 mils. If the wind speed is still increasing, then I'm going to hold at least 3.4 or 3.5 mils on the follow up shot. If it is dying down, I might hold 3.1 again.

Also, on my first shot, if the average speed is 25 mph and the wind speed is increasing as I need to break the shot, then I may hold 3.4 to center or 3.1 on the upwind edge. This would be more likely to keep the impact on the target as the wind speed increases. I would do the opposite if I felt the wind speed was decreasing.

One thing to note, at 25 mph it is likely that I might have to be much more aggressive with the lull and gust adjustments than stated above and I would base that off of watching impacts.

Also, in terms of error budget, a .6 mil target has a roughly 2 mph error budget for the wind call with a 4 mph gun.

Everything with a 6 mph gun would be similar, but slightly different numbers. 4th bracket (24 mph) at 500 yds is 2 mils plus 1mph additional is roughly +0.1mils for a 2.1 mil to center hold. The wind budget on a .6 mil target would be 3.6 mph or roughly 3 mph to keep you on the plate.

One thing I have thought about. From a numbers perspective, it makes sense to use a ballistic solver to get a solution in such high winds. Most guns are not a dead on 4 mph or 6 mph ect. That is the math guy coming out in me.

Now the realist. I have not written down a wind call in two seasons since learning this method from Frank and Mike on the podcast. In reality, I can not call the wind close enough at 25 mph to make the difference of having a 6 mph gun or a 6.3 mph gun matter. Also, most targets are large enough to eat the error. IN PRACTICE THIS STUFF JUST PLAIN WORKS. I do not need a solver to figure out a wind call and my ability to make first round impacts has increased tremendously. This has also helped greatly with correcting a poor initial wind call and then applying the corrected wind call to the remaining targets in the course of fire. The math is simple to break down and having a plan really helps turn a stage with a bad wind call into a stage with only a couple dropped points rather than a handful of dropped points.

This is one area where info from the podcast has truly been a game changer for me.