Aerodynamic jump, zero values and Calculators ?

[Subwrx300]

So after thinking through the concept of aerodynamic jump and zeroing, it seems like it *might* be a variable to account for (like AB and several others do). However, in AB specifically, there is no input for wind speed/direction during zero calculation.

As Frank has said several times over, if you are truly zeroed at 100 in any condition, your zero includes any aerodynamic jump. Without a wind condition (speed/heading) for a given new load profile and zero, this feature seems useless. It could potentially double the error by zeroing in one wind direction and shooting in the opposite.

I know the effects are minimal, but if you stack effects of mirage, coriolus, AJ, and spin drift (another debatable topic on magnitude of effect), those could easily add 1/2 - 1 MOA or ~.3 mil vs a correctly calibrated calculator solution (assuming all other inputs are as perfect as possible).

Do any programs allow this and/or, if not, why wouldn't they? If AJ is something that should be accounted for under a new environment, it seems super logical that it should be given an initial value during zero value as well.

Am I off base on this?

 

[_Windrider_]

At 100 yds, TOF is too short for AJ to be a factor. In addition, AJ really only plays in a full value wind condition. So when zeroing, it’s a non factor. The critical factor in zeroing is that you verify it’s a true 100yds from turret to Target, if it’s not make sure you put in 97 yds as your zero if it’s 97. Don’t use 100. In addition, if POA is different than POI you need to record that offset so it can be accounted for as well.

 

[Subwrx300]

At 100 yds, TOF is too short for AJ to be a factor. In addition, AJ really only plays in a full value wind condition. So when zeroing, it’s a non factor. The critical factor in zeroing is that you verify it’s a true 100yds from turret to Target, if it’s not make sure you put in 97 yds as your zero if it’s 97. Don’t use 100. In addition, if POA is different than POI you need to record that offset so it can be accounted for as well.

Hey TD, thanks for reply. I was asking a slightly different question than maybe you understood by my post. More of a "why the F$+# do solvers incorporate it without understanding the zering wind conditions?".

I understand what you mean and Ive read/researched AJ quite a bit over the last few weeks, but as I understand the mechanics, AJ happens right as bullet leaves muzzle encountering a crosswind (in any orientation U/D) by bullet point pitching up/down slightly and the angular deflection occurs as a result of the spin "climbing" or "diving" into cross wind. The displacement is established nearly immediately and deflection is then "set".

Here's a Hornady video on the topic (brief description a few seconds in): http://bulletin.accurateshooter.com/tag/aerodynamic-jump/

Here is artilce from @Lowlight about the Boatright-Ruiz method. (The link inside that page to the paper doesn't seem to work for me. ) https://www.snipershide.com/calcula...iring-point-conditions-boatright-ruiz-method/

I perfectly understand the need for a 100 yard zero; this is a given to minimize error down range.

My question is more about the logic for including AJ at all without an input for initial zero wind value.

Here's ABs description of it's engine features:

Their description (along with other definitions) show a direct angular displacement from the muzzle upon exit. So this is a "constant" value that depends on wind speed and direction relative to muzzle.

But if the solver is going to set a new value for AJ each time you input new conditions, it MUST need to know the initial value. If the calculation assumes you zeroed in no wind (absolutely no wind), then the calculation would be start with a true value of zero, then apply some correction for your current wind input and firing solution.

HOWEVER, if you zeroed in a 10mph cross wind, and bullets hit perfectly centered on POA, you would input no zero offset. But any AJ value would have to be present included in the "zero" you just shot.

Essentially, the initial value for aerodynamic jump can't always be zero. And without some input to determine how much of your zero is due to AJ effect (even if only .02MOA) the resulting calculations using your inputs will be wrong.

Aerodynamic Jump cannot be both irrelevant for zero AND relavent for a long range solution. Either Aerodynamic jump is present foe the first 100 yards (no matter how small) and it needs an "initial value" (just like zero offset, Muzzle velocity, BC etc). Then AB or Hornady or any solver with this feature could change the value in your new environment by the correct amount from your zeroing inputs.

OR ALTERNATIVELY: If the value is that small, there is no need to calculate it's effect in any part of the solution. In which case, why have it as a feature?

Hornady's solver has AJ included in it's engine too but I'm not sure how it differs in it's calculation from AB if at all.

Maybe that is the point being made by the math/engineering gurus on this site (@THEIS and @Jim Boatright I'm looking at you two?): the initial firing conditions are important, so knowing them as part of your zeroing conditions allows a solver to make better calculations. Does that help with my question?

 

[_Windrider_]

Understand but at 100 yds TOF is like what 4 hundredths of a second at 2800 FPS. Do you think that ever so slight of a yaw of a bullet has any effect downrange at 100 yds in that short of time?

My 65 creed is like .11 per 5 mph full value per 300 yds atarting at like 300 or so. Going off memory. The only app I know how to use that shows AJ is AB analytics and I don’t have it with me to do an example. @DocUSMCRetired can speak about AB better than me though.

But at 100 you are not seeing it.

 

[Subwrx300]

I

Understand but at 100 yds TOF is like what 4 hundredths of a second at 2800 FPS. Do you think that ever so slight of a yaw of a bullet has any effect downrange at 100 yds in that short of time?

My 65 creed is like .11 per 5 mph full value per 300 yds atarting at like 300 or so. Going off memory. The only app I know how to use that shows AJ is AB analytics and I don’t have it with me to do an example. @DocUSMCRetired can speak about AB better than me though.

But at 100 you are not seeing it.

I know what you are saying. In practice, I don't worry or think about AJ at all and likewise for Spin drift; that gets turned off.

If the AJ phenomena is non linear (has an actual zero - I mean ZERO) effect from say 0-100 yards, then suddenly kicks in at 101 yards or any number thereafter, you are completely correct.

But in terms of physics, that makes no sense. The effects of AJ may change have different values down range or at different speeds, but there is still an effect.

It would be like saying gravity has zero effect on bullet for the first .01 second after leaving muzzle. While it is really short time, an object in free fall would move ~.19 inches.

A better hypothetical example: You zero your rifle in a 25mph 90deg wind today because you have to (hunt/match/just because). Tomorrow you go to different range and hand your rifle + your calculator to another perfect shooter and conditions are 100% identical. They don't know your rifle so they plug in conditions for the day and put in 25mph wind so they know how much to hold/dial. The solver says 1 MOA/.3Mil right hold, they dial/hold, shoot and miss right. How could they miss if your rifle was zeroed at 100yds and effects of wind are small enough at that range to ignore, right? No; you already accounted for that 25mph wind.

If you reverse the 25mph wind (Left to Right) and they dial 1MOA/.3Mil left, they would still miss right. They would need 2 MOA to get rid of your wind zero and correct for current wind.

While the example is extreme and unlikely it's simply to illustrate that, at some point, variables in your zero matter even though we want to say "don't worry about; it it's too small at XXX distance." At some point for certain circumstances, it begins to matter or stack up and create a miss.

Again, I'm not questioning the practical side of this: zeroing on a calm day, we can hit our targets. Our data translates pretty well, and wind uncertainty makes it impossible hard to tell difference between .25moa zero error and 1mph wind read error at longer ranges.

But since a lot of solvers - if not most - have a "zero conditions" option that includes altitude, temperature, pressure, powder temp, etc. Why don't they include wind/speed at shooter. If a solver is supposed to help us learn and adapt to new conditions without shooting in them first, it would help to have wind added to zero conditions.

 

[_Windrider_]

AJ is a vertical component. It affects elevation not wind hold

 

[Subwrx300]

AJ is a vertical component. It affects elevation not wind hold

100% agree. My example was simply to show that at some point, things that don't matter begin to matter. I should probably rename thread "Why do solvers not include wind conditions for zero" because it's more about not having wind condition to determine wind component to elevation (AJ) and drift.

BTW good points all around and in practice we are on the same page.

 

[_Windrider_]

When I get home, I’ll show you in a range card from AB Analytics.

 

[Subwrx300]

I've got AB mobile not AB Analytics. I nearly bought ABA a while back but found AB Mobile to do a pretty good job although lacking WEZ and a few other cool features. I'm assuming that they have different inputs for zeroing which is why we are crossing back and forth on this. Looking forward to seeing the card.

 

[_Windrider_]

I've got AB mobile not AB Analytics. I nearly bought ABA a while back but found AB Mobile to do a pretty good job although lacking WEZ and a few other cool features. I'm assuming that they have different inputs for zeroing which is why we are crossing back and forth on this. Looking forward to seeing the card.

It’s the same, it ABA shows you exactly what SD is and AJ and all that.

 

[Subwrx300]

If you can see SD and AJ as independent values (broken out from rest of drop/drift component) then not the same on Android. The solutions will be the same I'm sure but the table looks different. Can't see those values in my table:

 

[_Windrider_]

If you can see SD and AJ as independent values (broken out from rest of drop/drift component) then not the same on Android. The solutions will be the same I'm sure but the table looks different. Can't see those values in my table:
View attachment 6955813

It’s not in the table. If you want a hold for a given shot, you type in that range and it gives you the solution but within that it shows you the components. Hard to explain, I’ll show you. Unless someone beats me to it

 

[Subwrx300]

So I pulled out my Kestrel 5700 AB to try a few things. It has individual components for AJ and drift.

If zero offset and zero height are zero (i.e. bullseye group center) and I set any wind value for baseline wind, Aerodynamic jump is present in my solution for even 100 yard zero. A 5mph wind at 3 o'clock shows elevation correction of .25MOA down. But would have just zeroed my rifle for those conditions so the solution is wrong. Same thing for windage: it shows a .27 MOA correction which I've just zeroed out of my system so I shouldn't need to dial anything.

The only way to remove this is to either zero in exactly 0 wind (impossible) OR offset my zero by the amount shown for the conditions I'm zeroing in. In this case, I would need to zero rifle .25moa low and .27moa right. Then my solution would be corrected for the environment and theoretically zeroed for all future conditions.

Happy to post photos if anyone needs them.

So, are there ANY apps or solvers that allow input of wind values for zeroing conditions or at least ignore aero jump/wind drift for zero conditions?

 

[_Windrider_]

Well. I guess a technique if you really want to get to it is figure out what your AJ is for the given wind conditions and when your POI differs by that much from your POA you are zeroed and AJ is not dialed out and you zero shift is still zero. Now theoretically your solution should be correct for any condition no? And in a zero wind it should be POA =. pOI right?

 

[Subwrx300]

Well. I guess a technique if you really want to get to it is figure out what your AJ is for the given wind conditions and when your POI differs by that much from your POA you are zeroed and AJ is not dialed out and you zero shift is still zero. Now theoretically your solution should be correct for any condition no? And in a zero wind it should be POA =. pOI right?

It might. I'll give it a test tomorrow morning. I wish there was a way to turn off AJ altogether just to check (like spin drift) Wind value 1 which seems to control AJ and lower wind hold, while Wind 2 controls only highest wind value.

 

[Kobyashi72]

Ballistic engines presuppose that gravity was the only influence present when the rifle was zeroed as it’s baseline zero reference and that the secondary effects of WIND shows up in the environment after the primary calculation of gravity was established.

The same way every user does when they set up their app. They check drop first. Then apply wind after.

The shooter would treat the 100 yard “zero” target just like He/She would at a 1000 yard target in a 10 mph wind. The shooter would “dial on” the correction before taking the shot. The shooter would continue to hold “Center” (cross-hair on the target) to hit POA/POI.

When zeroing the rifle in the cross-wind. The shooter would just be starting with the end result in mind and working backward to get the NO WIND zero.
(This presupposes the shooter inputed the latitude/azimuth and has spin drift enabled if it’s not being auto-calculated like Hornadys’ 4DOF or Lapaus’ 6DOF apps)

The shooter would adjust the turrets on the scope until He/She was hitting POA/POI at 100 yards in the current wind conditions.

Then enter the wind conditions present in the environment during the “zeroing process” in the solver and look at the solution at 100 yards.
(This presupposes that the solver is auto-calculating AJ into the solution. Like AB, Hornady 4DOF and Lapua Ballistics (6DOF))

(example. 10 mph wind from 9:00 @ 100yard. The solution presented by the solver is “0.1 U” mils for elevation and ”0.1L” mils for windage)

The Shooter would slip the scales on the turrets on the scope to read “0.1 U” on the elevation turret and ”0.1L” on the Windage turret.

That’s what the solver is presenting to the shooter to “Dial on” to the scope to hit “center” cross-hair at 100 yards in a 10 mph from 9:00 which is where the rifle is currently adjusted to in the present condition (hitting center cross-hair)


If the wind lulled to 0 mph or the shooter came out the next day and there was no wind blowing. The Shooter updates the input into the solver. The 100 yard solution would read “0” for Elevation and “0” for windage. The shooter would dial down 0.1 mils to “0” and dial 0.1 mils right to “0”


The scope is set to “0” and matches the the solver’s “zero” (both mechanical zero and the software zero are starting from the same baseline zero reference)


The shooter can now choose to “dial” the solution on and Hold “center” or leave the scope on “0” (hold-off/hold-over/hold-under) what ever the solver presents to the shooter.

 

[DocUSMCRetired]

AJ occurs during the first couple procession cycles. It does effect a 100 yard shot (because it happens near the muzzle). However with a 100 yard zero, a shooter should be able to remove this from the firing solution. The software itself will tell you what the AJ was, and you can simply slip it out of the turrets. Having an Aerodynamic Jump bias in the zero of the rifle can trick people into thinking "the firing solution" being spit out by the software always seems a little "off". when in reality the rifle is not truely zeroed. Now the software assume the shooter has given it a "perfect zero". And generally you shouldn't need to input zero atmosphere for a 100 yard zero.

The simple way to handle this, is when you zero to remove any AJ bias from the solution. You can do this one of two ways. The first is to pull the data from the software(if the software reports individual values) and reverse it. "I have a .25 MOA up correction, so I will just bring the zero down .25MOA so that it impacts at zero with 0.25MOA Up adjustment on the turret". Or you can run the firing solution at the time, and reverse that.

The reality is, this can be "lost in the noise" for many shooters. If thats MV shift with temp, or zero shift by shooting off different platforms (going from concrete to grass). Maybe its the calibration factor of the scopes turrets. But once you get into LR and ELR shooting it can become more important. Of course this can also be more or less valuable if the shooter zeroed in a 25mph wind vs doing it in a 2mph wind. So it is important to weigh it against everything.

 

[Subwrx300]

AJ occurs during the first couple procession cycles. It does effect a 100 yard shot (because it happens near the muzzle). However with a 100 yard zero, a shooter should be able to remove this from the firing solution. The software itself will tell you what the AJ was, and you can simply slip it out of the turrets. Having an Aerodynamic Jump bias in the zero of the rifle can trick people into thinking "the firing solution" being spit out by the software always seems a little "off". when in reality the rifle is not truely zeroed. Now the software assume the shooter has given it a "perfect zero". And generally you shouldn't need to input zero atmosphere for a 100 yard zero.

The simple way to handle this, is when you zero to remove any AJ bias from the solution. You can do this one of two ways. The first is to pull the data from the software(if the software reports individual values) and reverse it. "I have a .25 MOA up correction, so I will just bring the zero down .25MOA so that it impacts at zero with 0.25MOA Up adjustment on the turret". Or you can run the firing solution at the time, and reverse that.

The reality is, this can be "lost in the noise" for many shooters. If thats MV shift with temp, or zero shift by shooting off different platforms (going from concrete to grass). Maybe its the calibration factor of the scopes turrets. But once you get into LR and ELR shooting it can become more important. Of course this can also be more or less valuable if the shooter zeroed in a 25mph wind vs doing it in a 2mph wind. So it is important to weigh it against everything.

Hey Doc, thank you for the reply. Your answer makes complete semse.

I run both AB mobile and the AB Kestrel Elite 5700. Am I correct that AB Mobile does not show the AJ value? If so, how would I correct out the AJ value from mobile app? I presume I would need to subtract/add the Kestrel output for the day, correct? Or is there another way to find it in Mobile app?

Would AB be open to idea of a wind condition for zero? It is much easier to have software reverse out the components like drift and AJ internally versus shooting and slipping turrets. I totally understand the possibility to have the actual values get lost in the noise of measurement error; it just seems like a better process to shoot, input environment and wind and then have a new output that is value for all future solutions without messing with turrets or subtracting drift/drop changes after the fact.

Also, shot Sunday and Kestrel values with same inputs were nearly perfect and required very little correction (less than .2 in most targets out to 900 and less than .4 moa out from 900 to 1060). But with same profile (sight, velocity, BC, zero, environment, SD, Coriolus, and distance) in AB Mobile, needed more like .5 to 1Moa depending on distance.

Truing AB Mobile via 2 ranges (800 and 1058) it corrected MV and BC values much more. Do the two apps handle the solutions slightly differently?

It was much easier to get the corrected output with Kestel BUT it's much more convenient to build tables and cards with mobile app. Is there a better way to reconcile the two apps? I trust the Kestrel to get me very close a bit more than app. I've running app for better part of last 7 years, so I'd like to find a good way to marry the two for ease of use and outputting data for various scenarios.

Thanks in advance for the reply!

 

[DocUSMCRetired]

Hey Doc, thank you for the reply. Your answer makes complete semse.

I run both AB mobile and the AB Kestrel Elite 5700. Am I correct that AB Mobile does not show the AJ value? If so, how would I correct out the AJ value from mobile app? I presume I would need to subtract/add the Kestrel output for the day, correct? Or is there another way to find it in Mobile app?

Would AB be open to idea of a wind condition for zero? It is much easier to have software reverse out the components like drift and AJ internally versus shooting and slipping turrets. I totally understand the possibility to have the actual values get lost in the noise of measurement error; it just seems like a better process to shoot, input environment and wind and then have a new output that is value for all future solutions without messing with turrets or subtracting drift/drop changes after the fact.

Also, shot Sunday and Kestrel values with same inputs were nearly perfect and required very little correction (less than .2 in most targets out to 900 and less than .4 moa out from 900 to 1060). But with same profile (sight, velocity, BC, zero, environment, SD, Coriolus, and distance) in AB Mobile, needed more like .5 to 1Moa depending on distance.

Truing AB Mobile via 2 ranges (800 and 1058) it corrected MV and BC values much more. Do the two apps handle the solutions slightly differently?

It was much easier to get the corrected output with Kestel BUT it's much more convenient to build tables and cards with mobile app. Is there a better way to reconcile the two apps? I trust the Kestrel to get me very close a bit more than app. I've running app for better part of last 7 years, so I'd like to find a good way to marry the two for ease of use and outputting data for various scenarios.

Thanks in advance for the reply!

I am going to try my best to break this post down into bullet points.

1) AB Mobile does not output AJ, however if you do a firing solution at 100 yards (with a 100 yard zero) or look at the table at 100 yards you can see the offset AJ has created.

2) I can always share suggestions with the team.

3) Both of them should be within 1 or 2 clicks of each other at most. If they are off by 1/2 a minute that means something else (maybe a pressure change occurred that the Kestrel saw) is going on.

4) The two devices handle things the same way. The only difference is the user gets to pick on the Kestrel. The App automatically does block one as MV and block 2+3 as DSF. Where on the Kestrel you can pick either MV or DSF.

5) You should have the ability now to build your own tables on the Kestrel and print them.

 

[Subwrx300]

Perfect reply! Thank you!