Simple adjustment for wind drift ?

[follow maggie]

I'm pretty simple. If the wind is blowing to bend the grass, I hold into it about 2". If the wind isn't bending the grass I just hold dead on. I've never shot an animal more than woo yards, so this has always worked great for me.

[Yondering]

Better have your windage turret marked for the actual zero.  Otherwise you won't be able to tell what the "non wind" zero is.   

I'm not sure I understand what the advice here is for, as it seems painfully obvious so I must be missing something. Do your turrets not have zero marks on them? And do you not set initial zero in no-wind situations?

All of my turrets have zero marks, and the turrets are reset to those marks after zeroing the rifle.

I prefer to hold in the wind too, my example above was for simplicity for the OP.

[Miles]

Turrets...where's all the fun in that?  I've got the simplest windage and elevation adjustments.  It's called hold over, compensate for wind, and pray.   Maybe not the best, but as the title requests, it's simple.




In all seriousness, turrets are in my near future. 

[jay.sharkbait]

I think wind calls are too dynamic to dial.

Taking your head out of the rifle ( physically and mentally) takes too much time.

[SilkOnTheDrySide]

I think wind calls are too dynamic to dial.

Taking your head out of the rifle ( physically and mentally) takes too much time.

Not to mention I've seen wind go from 1 MIL-2, back to 1.5 and steady on 1.

Can you imagine the ridiculousness of jumping in and out to make adjustments?

I set my wind to 10, it's linear. If you have a 1 MIL hold and the wind is 5 MPH, it becomes a .5 MIL hold.  Additionally if it's a 45 degree wind, it's a .25 MIL hold.

See! Wind is easy!


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[Bill W]

on the side winds.... how do you factor in whether the side wind is causing the bullet to rotate up.... or down if it's from the other direction?

I remember when wind was simple, just hold off a touch.  But then when the desire was to hit the bullseye dead center, reading the wind got a lot harder.    I shoot cast bullets out of a .30 BR and because of the lower velocity of lead bullets and poorer ballistic coefficient reading the wind is a graduate level course.   I shot one winter with the jacket bullet crowd as i thought they had a better handle on evaluating wind flags and found out that jacketed bullets were so much easier to shoot accurately.  The BC is so much higher and the velocity is at least 1200 fps faster.

But in a cross wind and depending on which way the twist in the barrel is, the bullets either rise up somewhat, or are pushed down based on wind direction.

[high country]

on the side winds.... how do you factor in whether the side wind is causing the bullet to rotate up.... or down if it's from the other direction?

I remember when wind was simple, just hold off a touch.  But then when the desire was to hit the bullseye dead center, reading the wind got a lot harder.    I shoot cast bullets out of a .30 BR and because of the lower velocity of lead bullets and poorer ballistic coefficient reading the wind is a graduate level course.   I shot one winter with the jacket bullet crowd as i thought they had a better handle on evaluating wind flags and found out that jacketed bullets were so much easier to shoot accurately.  The BC is so much higher and the velocity is at least 1200 fps faster.

But in a cross wind and depending on which way the twist in the barrel is, the bullets either rise up somewhat, or are pushed down based on wind direction.

The values and math are the same, just the method of horizontal compensation changes. I still run the numbers, but instead of holding zero and making a .7 mil corrrection it's in the scope. You either have to be a memory master, or have a ballistic solver handy.

[Bill W]

on the side winds.... how do you factor in whether the side wind is causing the bullet to rotate up.... or down if it's from the other direction?

I remember when wind was simple, just hold off a touch.  But then when the desire was to hit the bullseye dead center, reading the wind got a lot harder.    I shoot cast bullets out of a .30 BR and because of the lower velocity of lead bullets and poorer ballistic coefficient reading the wind is a graduate level course.   I shot one winter with the jacket bullet crowd as i thought they had a better handle on evaluating wind flags and found out that jacketed bullets were so much easier to shoot accurately.  The BC is so much higher and the velocity is at least 1200 fps faster.

But in a cross wind and depending on which way the twist in the barrel is, the bullets either rise up somewhat, or are pushed down based on wind direction.

The values and math are the same, just the method of horizontal compensation changes. I still run the numbers, but instead of holding zero and making a .7 mil corrrection it's in the scope. You either have to be a memory master, or have a ballistic solver handy.

I wondered if you long range jacketed bullet shooters knew about this.   It needs to be factored in if one is trying for a dead center or "pinwheel" bullseye.     Depending on which way the rifling goes and which way the wind is blowing the bullet is either pushed up/or down in a side wind.

Did a search on external ballistics and came up with another on head/tail winds.    This made me pull out hair at times during matches as the degree of difficulty is about 10 time more when shooting cast bullet benchrest.   Here's the info below.

Magnus effect[edit]

The Magnus effect. V represents the wind, the arrow F is the resulting Magnus force towards the side of lower pressure.
Spin stabilized projectiles are affected by the Magnus effect, whereby the spin of the bullet creates a force acting either up or down, perpendicular to the sideways vector of the wind. In the simple case of horizontal wind, and a right hand (clockwise) direction of rotation, the Magnus effect induced pressure differences around the bullet cause a downward (wind from the right) or upward (wind from the left) force viewed from the point of firing to act on the projectile, affecting its point of impact.[60] The vertical deflection value tends to be small in comparison with the horizontal wind induced deflection component, but it may nevertheless be significant in winds that exceed 4 m/s (14.4 km/h or 9 mph).

Magnus effect and bullet stability[edit]
The Magnus effect has a significant role in bullet stability because the Magnus force does not act upon the bullet's center of gravity, but the center of pressure affecting the yaw of the bullet. The Magnus effect will act as a destabilizing force on any bullet with a center of pressure located ahead of the center of gravity, while conversely acting as a stabilizing force on any bullet with the center of pressure located behind the center of gravity. The location of the center of pressure depends on the flow field structure, in other words, depending on whether the bullet is in supersonic, transonic or subsonic flight. What this means in practice depends on the shape and other attributes of the bullet, in any case the Magnus force greatly affects stability because it tries to "twist" the bullet along its flight path.[61][62]

Paradoxically, very-low-drag bullets due to their length have a tendency to exhibit greater Magnus destabilizing errors because they have a greater surface area to present to the oncoming air they are travelling through, thereby reducing their aerodynamic efficiency. This subtle effect is one of the reasons why a calculated Cd or BC based on shape and sectional density is of limited use.

Poisson effect[edit]
Another minor cause of drift, which depends on the nose of the projectile being above the trajectory, is the Poisson Effect. This, if it occurs at all, acts in the same direction as the gyroscopic drift and is even less important than the Magnus effect. It supposes that the uptilted nose of the projectile causes an air cushion to build up underneath it. It further supposes that there is an increase of friction between this cushion and the projectile so that the latter, with its spin, will tend to roll off the cushion and move sideways.

This simple explanation is quite popular. There is, however, no evidence to show that increased pressure means increased friction and unless this is so, there can be no effect. Even if it does exist it must be quite insignificant compared with the gyroscopic and Coriolis drifts.

Both the Poisson and Magnus Effects will reverse their directions of drift if the nose falls below the trajectory. When the nose is off to one side, as in equilibrium yaw, these effects will make minute alterations in range.

[Henrydog]

There is also the Coriolis effect.  In the Northern Hemisphere the longer the object is in flight the more off to the right it will be at the target.  Same reason all toilets flush clockwise.  Just the reverse in the Southern Hemisphere.  The French Military noticed it when artillery improved in the mid 1830's.   

I've never noticed it when shooting my 45/70 with open sites

[Miles]

You guys are overthinking things...

[high country]

If you can shoot into the hundredth it's super important.....

[jackelope]

Starting to realize the simple fact that I'm not detail oriented enough to be a long range shooter.

[trophyhunt]

Starting to realize the simple fact that I'm not detail oriented enough to be a long range shooter.

My huskemaw must be easier to shoot than most other long range scopes, about my only math is, how hard is the wind blowing?  If no wind, my confidence is pretty high at a long range.  The wind-age marks are set for 10 mph increments, maybe I'm not doing it right but at 650 or whatever yardage its at,  I set my turret and put the cross hairs on the sweet spot and shoot.  I've been with guys that had the math stuff taped to their scope, get the distance and then start doing the math???  In the mean time, the 6 point walk out of the area.

[jay.sharkbait]

Starting to realize the simple fact that I'm not detail oriented enough to be a long range shooter.

Don't let some of this stuff intimidate you.

I think the biggest thing is the wind call. Not just the wind at the shooters position, but wind down range. You really don't need a kestrel you just need to be able to look at mirage, vegetation, water etc and you can make very accurate calls based on that.

Temp, pressure and Spin drift is simple to account for and use.

Coriolis is something I'm too lazy to care about. That said it does come into play at a mile or more and is something you have to factor at 2 miles and keep in mind, it changes depending on the shot direction.

All the other stuff is fluff IMHO.

[high country]

Just plugging the numbers in for my 260ai with rdf's, @ 700yds there's a 4" vertical difference between a right and left wind and a 6" horizontal hold difference between the right and left. These are all with a 10mph wind.

If you shoot long, the details matter. You can still use a reticle, but understand the thing is just a tape measure and you choose the numbers.