Applied ballistics zero and Barometric pressure question

[chukwithak]

I'm used to 4DOF which takes in the BM when you zero. Thus if you climb altitude your zero is adjusted to the pressure. How does Applied Ballistics figure this out and compensate for your zero? I'm trying to tell my self to make the switch because of availability in products, but I'm not understanding how AB knows. Even if I shoot at the same location, different BM's are going to provide different results.

Even if the computer knows what the BM is with all of the data in the world, it doesnt know what my zero is. Make it make sense, please....

 

[Formidilosus]

I'm used to 4DOF which takes in the BM when you zero. Thus if you climb altitude your zero is adjusted to the pressure. How does Applied Ballistics figure this out and compensate for your zero? I'm trying to tell my self to make the switch because of availability in products, but I'm not understanding how AB knows. Even if I shoot at the same location, different BM's are going to provide different results.

Even if the computer knows what the BM is with all of the data in the world, it doesnt know what my zero is. Make it make sense, please....

A 100 yard zero in Death Valley, is a 100 yard zero on top of Mount Everest. 100 yard POI does not change with carrying weather and atmosphere.

 

[chukwithak]

A 100 yard zero in Death Valley, is a 100 yard zero on top of Mount Everest. 100 yard POI does not change with carrying weather and atmosphere.

But is a 100yrd zero in Death Valley a bullseye at 800 yards with a ballistic calculator on Mt Everest?

 

[just.mark]

I have asked this myself and for the life of me I can't reason it out to make it make sense.

And then i read this thread: https://www.longrangeonly.com/forum/threads/ballistic-apps-zeros-and-changing-altitude.1946/


Now I am questioning continuing to use a 200 yard zero.

 

[Shortschaf]

But is a 100yrd zero in Death Valley a bullseye at 800 yards with a ballistic calculator on Mt Everest?

The "zero atmosphere" gives the calculator the ability to compare the atmosphere at the time you zeroed to another atmosphere.

But this is only used to predict and correct for a change in your ZERO due to atmosphere. If there is no calculated change in zero, there will be no downstream change in the dope at some range.

As Formidilosus mentioned above--100 yard zeros are such short-range that they are unaffected by even the craziest changes of atmosphere. It is a big reason why people use 100 yard zeros to begin with.

Since you are using a 100 yard zero, just disable the "zero atmosphere" and see for yourself if it changes any dope at any range at all. Or go in and play with the zero-pressures and zero-temperatures to very different values and see if it changes your dope.

 

[Formidilosus]

But is a 100yrd zero in Death Valley a bullseye at 800 yards with a ballistic calculator on Mt Everest?

The zero doesn’t change at 100 yards, your predicted data for 800 yards changes and you get that by putting in the environmentals when you are standing on Everest.

 

[chukwithak]

Ok, last question. If I'm using the Vortex Fury with AB and and a Kestrel with AB, there's no need for the $30 app correct?

I'm going to just pull the trigger and put some faith in it. Messing with 4DOF I discovered that when you change the environments that it changes the environments in the zero angle too. Which makes this makes sense. I cant figure out why hornady would put that in the zero if it changes.

 

[Harvey_NW]

Ok, last question. If I'm using the Vortex Fury with AB and and a Kestrel with AB, there's no need for the $30 app correct?

I'm going to just pull the trigger and put some faith in it. Messing with 4DOF I discovered that when you change the environments that it changes the environments in the zero angle too. Which makes this makes sense. I cant figure out why hornady would put that in the zero if it changes.

4DOF does some goofy things, like pretty drastic changes to elevation when you add a couple MPH of wind. I've been playing with it for a while and it doesn't quite translate into reality, for me. What I can tell you, is I recently took the same step with AB and a Sig Kilo 5K. I feel like the biggest smooth brain ever for not buying one sooner. It was the easiest setup I've ever done, and it was spot on. No truing, no fiddling, just plug in correct inputs and velocity data from chrono, and whack targets. Highly suggest trusting AB.

 

[Shortschaf]

For what it is worth:
AB is good enough that I've purchased it 3 times going from Apple to Samsung back to Apple

 

[philcox]

A 100 yard zero in Death Valley, is a 100 yard zero on top of Mount Everest. 100 yard POI does not change with carrying weather and atmosphere.

@Formidilosus this is counter intuitive to me, as things definitely change in Archery. It this fact based on the change of POI @ 100y DV -> ME is imperceivable?

 

[Formidilosus]

@Formidilosus this is counter intuitive to me, as things definitely change in Archery. It this fact based on the change of POI @ 100y DV -> ME is imperceivable?

Does your 10 yard zero change with your bow in different atmospheres?

 

[philcox]

Does your 10 yard zero change with your bow in different atmospheres?

Technically it probably does (air density and drag), but it to your point it does not in any perceivable manner. Any change is well within my variability of putting an arrow at center

 

[wind gypsy]

Technically it probably does (air density and drag), but it to your point it does not in any perceivable manner. Any change is well within my variability of putting an arrow at center

Something moving at 270 FPS has a much different trajectory at 100 yards than something at 3000 FPS.

 

[Formidilosus]

Technically it probably does (air density and drag), but it to your point it does not in any perceivable manner. Any change is well within my variability of putting an arrow at center

I’m sure it does- about a thousandth of an inch.

A 100 yard zero is a 100 yard zero anywhere on earth.

 

[khuber84]

The guys I know that push 4dof saying it's better system, are Hornady sponsored shooters/instructors. The systems will give the same data for most part. Cept 4dof is flawed in high angle shots. I forget whether it's the high angle incline or decline elevation, but ones way jacked. I have both kestrels, they both work. 4dof has way less bullets in their library that are no Hornady. I hear 4dof is getting a big upgrade, but so is AB.

 

[philcox]

This has been an interesting thread, and honestly a bit confusing in practice. I am using both Shooter and Revic apps to determine "drops". With the exact same inputs (or as best I can)
- 135 DRT G1 .475 @ 2905, 100y zero
- Altitude 3500, temp 90deg (Revic give me a calc pressure of 26.3 inHg, and off DA chart, I estimate a DA of 6500 for Shooter). They are both the same until 500y where they deviate. It's only really .01mil, but I would think the should be the same. Is the likely culprit that my DA estimate off the chart is wrong?

I get the following from the Drop Values (mil):

Distance	Shooter	Revic
200	.4	.4
300	1.0	1.0
400	1.7	1.7
500	2.5	2.55 (2.6)
600	3.4	3.45 (3.5)

 

[Formidilosus]

This has been an interesting thread, and honestly a bit confusing in practice. I am using both Shooter and Revic apps to determine "drops". With the exact same inputs (or as best I can)
- 135 DRT G1 .475 @ 2905, 100y zero
- Altitude 3500, temp 90deg (Revic give me a calc pressure of 26.3 inHg, and off DA chart, I estimate a DA of 6500 for Shooter). They are both the same until 500y where they deviate. It's only really .01mil, but I would think the should be the same. Is the likely culprit that my DA estimate off the chart is wrong?

I get the following from the Drop Values (mil):

Distance	Shooter	Revic
200	.4	.4
300	1.0	1.0
400	1.7	1.7
500	2.5	2.55 (2.6)
600	3.4	3.45 (3.5)

That is a rounding error.