Why Gravity Ballistics?

[Emerson0311]

So like basic old school dope collection without factoring in environmentals?

 

[Baron23]

I have been reading a bunch of posts on GB and the more things like this that I read the more I believe the people who developed GB don’t actually understand how to use a ballistic solver. And because they can’t use a ballistic solver like AB they have developed the most simplistic and asinine way of figuring out “try data” as they like to say. The original poster stated that he can basically zero at 100m, then take shots at 500 and 1000 and have his ballistic silver trued. Which means that his ballistic solver will have accurate holds for any distance out to subsonic and you claim that he wastes too much time in his solver? You waste way more time firing at every even hundred yard line and doing your GB math which will inevitably almost always be wrong. Maybe it won’t be wrong enough to put you off target (depending on the size of the target) but it will still be wrong. There are so many more things than gravity that matter and the way you are selling this does a huge disservice to those that want to be able to go out and shoot accurately at varying distances. Here’s a simple example: if someone use your GB for a 6.5CM on their “home range” and it is 60 degrees outside their data at 1000 will be 10.7 mils. So they went thru your ridiculous table and wasted a minimum of 20 rounds (if everything works out perfectly and they get 2 solid hits on the waterline using your math) getting all of their “non-theoretical” real-life hits at every even hundred yard line. So the shooter now has everything written down and “knows” that 10.7 mils gets hits at 1000m. Now he comes back to his “home range” and goes to shoot at the same 1000m target and puts 10.7 mils on it and misses high because the temperature is now 90 degrees and he only needs to hold 10.3 mils to hit the 12” circle at 1000m. And high misses are always harder to see than low misses, so he might just think it’s wind to begin with because you claim this GB works. And then he wastes a bunch more shots before he figures it out. Whereas if the shooter just learned how to use a ballistic solver and use it correctly, he wouldn’t have this issue. I have been shooting for 2 decades, and however this might have been useful 2 decades ago, it is utterly ridiculous to pretend that this is something that plays any role in shooting today. I am a huge fan of Applied Ballistics, but I would be willing to say that any notable ballistics solver is better than this. Just pick one and learn how to use it (AB, GeoBallistics, strelok, 4dof) and you will never go wrong. Ballistic solvers aren’t theory, this stupid GB is “theory”. Ballistics solvers use advanced equations of projectiles in motion to develop a ballistic trajectory and they do it extremely well. There’s a reason special operations use Applied Ballistics; it’s because it works to give you a solution that will hit your target. Ballistic solvers take into account temperature, humidity, barometric pressure, the zero distance, muzzle velocity, bullet weight, diameter and form factor (shape), ballistic coefficient, gyroscopic stability, angle of attack of the projectile, pitch, yaw, aerodynamic jump, wind, inclination angle, air density, etc. Ballistic solvers work, you put in good information and they spit out good holds, period. Don’t let people who developed a poor idea to help them boost their teaching career and make money off of the poor idea tell you that ballistic solvers are some useless “theory” and act as if their simple math is going to save you time and ammunition. Because it won’t, ballistic solvers that are used properly will save you much more time and ammunition over the ridiculous Gravity Ballistics 3rd grade math problem. Ballistic solvers will also help you miss less, allow you to compare different calibers, bullets, muzzle velocities, etc without ever even having to fire a shot. You can also use them to see how different variables will affect your holds. Ballistic solvers have so many uses that you could literally write a book talking about all of the advantages of them.

Carriage Return is your friend. ;-) lol

 

[Baron23]

Wait...WAIT...though nobody wants to read your wall of text:

I believe the people who developed GB don’t actually understand how to use a ballistic solver. And because they can’t use a ballistic solver like AB they have developed the most simplistic and asinine way of figuring out “try data” as they like to say.

You are actually saying that Frank Galli and Marc Taylor don't know how to use a ballistic solver...AB or any other damn one? You actually said that?

 

[Makinchips208]

So like basic old school dope collection without factoring in environmentals?

Kinda correct. You can enter the density altitude in low, med, high, as well as record the temperature. Neither of which do anything to the calculation, if I heard Lowlight correct in the podcast.

@Enough Said is that correct? Maybe a note section to record the atmospherics more specifically? Thoughts?

 

[Enough Said]

I have been reading a bunch of posts on GB and the more things like this that I read the more I believe the people who developed GB don’t actually understand how to use a ballistic solver. And because they can’t use a ballistic solver like AB they have developed the most simplistic and asinine way of figuring out “try data” as they like to say. The original poster stated that he can basically zero at 100m, then take shots at 500 and 1000 and have his ballistic silver trued. Which means that his ballistic solver will have accurate holds for any distance out to subsonic and you claim that he wastes too much time in his solver? You waste way more time firing at every even hundred yard line and doing your GB math which will inevitably almost always be wrong. Maybe it won’t be wrong enough to put you off target (depending on the size of the target) but it will still be wrong. There are so many more things than gravity that matter and the way you are selling this does a huge disservice to those that want to be able to go out and shoot accurately at varying distances. Here’s a simple example: if someone use your GB for a 6.5CM on their “home range” and it is 60 degrees outside their data at 1000 will be 10.7 mils. So they went thru your ridiculous table and wasted a minimum of 20 rounds (if everything works out perfectly and they get 2 solid hits on the waterline using your math) getting all of their “non-theoretical” real-life hits at every even hundred yard line. So the shooter now has everything written down and “knows” that 10.7 mils gets hits at 1000m. Now he comes back to his “home range” and goes to shoot at the same 1000m target and puts 10.7 mils on it and misses high because the temperature is now 90 degrees and he only needs to hold 10.3 mils to hit the 12” circle at 1000m. And high misses are always harder to see than low misses, so he might just think it’s wind to begin with because you claim this GB works. And then he wastes a bunch more shots before he figures it out. Whereas if the shooter just learned how to use a ballistic solver and use it correctly, he wouldn’t have this issue. I have been shooting for 2 decades, and however this might have been useful 2 decades ago, it is utterly ridiculous to pretend that this is something that plays any role in shooting today. I am a huge fan of Applied Ballistics, but I would be willing to say that any notable ballistics solver is better than this. Just pick one and learn how to use it (AB, GeoBallistics, strelok, 4dof) and you will never go wrong. Ballistic solvers aren’t theory, this stupid GB is “theory”. Ballistics solvers use advanced equations of projectiles in motion to develop a ballistic trajectory and they do it extremely well. There’s a reason special operations use Applied Ballistics; it’s because it works to give you a solution that will hit your target. Ballistic solvers take into account temperature, humidity, barometric pressure, the zero distance, muzzle velocity, bullet weight, diameter and form factor (shape), ballistic coefficient, gyroscopic stability, angle of attack of the projectile, pitch, yaw, aerodynamic jump, wind, inclination angle, air density, etc. Ballistic solvers work, you put in good information and they spit out good holds, period. Don’t let people who developed a poor idea to help them boost their teaching career and make money off of the poor idea tell you that ballistic solvers are some useless “theory” and act as if their simple math is going to save you time and ammunition. Because it won’t, ballistic solvers that are used properly will save you much more time and ammunition over the ridiculous Gravity Ballistics 3rd grade math problem. Ballistic solvers will also help you miss less, allow you to compare different calibers, bullets, muzzle velocities, etc without ever even having to fire a shot. You can also use them to see how different variables will affect your holds. Ballistic solvers have so many uses that you could literally write a book talking about all of the advantages of them.

You must be the guy we use as an example in the classroom who claims to know his data "without ever firing a shot". We'll refer to you as @Tolman1042 from now on and you'll be famous.

@Lowlight, we found him. LOL

We got tired of shooters, like yourself, who never took the time to understand that gathering data is a process and the better you understand that process, the better shooter you will become. They just want to jump to the solution with no understanding of it.

We all use solvers. But only after the solver has been trued to actual data, because that is part of the process.. I'm sure you skipped that step, "without ever firing a shot", but that's on you. While you're at it, skip the honing of fundamentals too. You'll be making wind calls in no time, with no realization that your trigger "crush or "slap" was part of your wind problem all along.

Introduce a double-digit standard deviation and your solver-gathered solution falls apart again. Lots of pieces to your puzzle, and you must understand them all.

What we offer is a simple approach to gathering data in order that you may move forward with your understanding of the process. And it doesn't care what your muzzle velocity is.

Oh... You'd better know your data and be able to get a solution without that phone from here forward or you may hear a drone hovering over your head. The battlefield is changing fast. SpecOps is learning this.

---Marc Taylor

 

[Emerson0311]

You must be the guy we use as an example in the classroom who claims to know his data "without ever firing a shot". We'll refer to you as @Tolman1042 from now on and you'll be famous.

@Lowlight, we found him. LOL

We got tired of shooters, like yourself, who never took the time to understand that gathering data is a process and the better you understand that process, the better shooter you will become. They just want to jump to the solution with no understanding of it.

We all use solvers. But only after the solver has been trued to actual data, because that is part of the process.. I'm sure you skipped that step, "without ever firing a shot", but that's on you. While you're at it, skip the honing of fundamentals too. You'll be making wind calls in no time, with no realization that your trigger "crush or "slap" was part of your wind problem all along.

Introduce a double-digit standard deviation and your solver-gathered solution falls apart again. Lots of pieces to your puzzle, and you must understand them all.

What we offer is a simple approach to gathering data in order that you may move forward with your understanding of the process. And it doesn't care what your muzzle velocity is.

Oh... You'd better know your data and be able to get a solution without that phone from here forward or you may hear a drone hovering over your head. The battlefield is changing fast. SpecOps is learning this.

---Marc Taylor

Sound. I find that lots trigger time on paper brings me back around to clean up the sloppy and inaccurate data I used originally to get close. For me, there is no shortcut to making an effective wind call. Rounds downrange in wind while attempting to make some sense of where they go seems to be the only way for me to learn. It helps to watch someone better than I, although even then progress is slow.

 

[Enough Said]

Kinda correct. You can enter the density altitude in low, med, high, as well as record the temperature. Neither of which do anything to the calculation, if I heard Lowlight correct in the podcast.

@Enough Said is that correct? Maybe a note section to record the atmospherics more specifically? Thoughts?

Correct. You are only noting the DA at the time you gathered the data , it is not a factor of creating the data.

 

[Enough Said]

So like basic old school dope collection without factoring in environmentals?

Yes, but with a very predictable outcome. Much more efficient.

 

[Long Range 338]

I have been reading a bunch of posts on GB and the more things like this that I read the more I believe the people who developed GB don’t actually understand how to use a ballistic solver. And because they can’t use a ballistic solver like AB they have developed the most simplistic and asinine way of figuring out “try data” as they like to say. The original poster stated that he can basically zero at 100m, then take shots at 500 and 1000 and have his ballistic silver trued. Which means that his ballistic solver will have accurate holds for any distance out to subsonic and you claim that he wastes too much time in his solver? You waste way more time firing at every even hundred yard line and doing your GB math which will inevitably almost always be wrong. Maybe it won’t be wrong enough to put you off target (depending on the size of the target) but it will still be wrong. There are so many more things than gravity that matter and the way you are selling this does a huge disservice to those that want to be able to go out and shoot accurately at varying distances. Here’s a simple example: if someone use your GB for a 6.5CM on their “home range” and it is 60 degrees outside their data at 1000 will be 10.7 mils. So they went thru your ridiculous table and wasted a minimum of 20 rounds (if everything works out perfectly and they get 2 solid hits on the waterline using your math) getting all of their “non-theoretical” real-life hits at every even hundred yard line. So the shooter now has everything written down and “knows” that 10.7 mils gets hits at 1000m. Now he comes back to his “home range” and goes to shoot at the same 1000m target and puts 10.7 mils on it and misses high because the temperature is now 90 degrees and he only needs to hold 10.3 mils to hit the 12” circle at 1000m. And high misses are always harder to see than low misses, so he might just think it’s wind to begin with because you claim this GB works. And then he wastes a bunch more shots before he figures it out. Whereas if the shooter just learned how to use a ballistic solver and use it correctly, he wouldn’t have this issue. I have been shooting for 2 decades, and however this might have been useful 2 decades ago, it is utterly ridiculous to pretend that this is something that plays any role in shooting today. I am a huge fan of Applied Ballistics, but I would be willing to say that any notable ballistics solver is better than this. Just pick one and learn how to use it (AB, GeoBallistics, strelok, 4dof) and you will never go wrong. Ballistic solvers aren’t theory, this stupid GB is “theory”. Ballistics solvers use advanced equations of projectiles in motion to develop a ballistic trajectory and they do it extremely well. There’s a reason special operations use Applied Ballistics; it’s because it works to give you a solution that will hit your target. Ballistic solvers take into account temperature, humidity, barometric pressure, the zero distance, muzzle velocity, bullet weight, diameter and form factor (shape), ballistic coefficient, gyroscopic stability, angle of attack of the projectile, pitch, yaw, aerodynamic jump, wind, inclination angle, air density, etc. Ballistic solvers work, you put in good information and they spit out good holds, period. Don’t let people who developed a poor idea to help them boost their teaching career and make money off of the poor idea tell you that ballistic solvers are some useless “theory” and act as if their simple math is going to save you time and ammunition. Because it won’t, ballistic solvers that are used properly will save you much more time and ammunition over the ridiculous Gravity Ballistics 3rd grade math problem. Ballistic solvers will also help you miss less, allow you to compare different calibers, bullets, muzzle velocities, etc without ever even having to fire a shot. You can also use them to see how different variables will affect your holds. Ballistic solvers have so many uses that you could literally write a book talking about all of the advantages of them.

The most ironic part is that you took the time to post such a long drawn out trashing of Gravity Ballistics but didn’t bother to understand how it works and why it’s useful. Nobody ever said it’s a complete replacement for a ballistic solver…

 

[Enough Said]

Tolman1042 is nothing but a troll.

 

[ScPiper]

Not to dredge up an older post, but for clarity's sake, can the GB app be used to true up the 4Dof ballistic solver app? if so, how would that process look?

 

[Enough Said]

Yes.
True the M/V in 4Dof, or any solver, to your observed GB drop (data) at 600 until that solver gives you the same drop data as GB at 600. Then manipulate your BC in the solver until it gives you your observed hit data at 800 , or even better 1000. Slight nudge to the middle BC digit is all it takes.

Once this is done, your solver is now extremely reliable data , based on actual hits, with somewhat of a custom drag curve.

 

[Baron23]

Yes.
True the M/V in 4Dof, or any solver, to your observed GB drop (data) at 600 until that solver gives you the same drop data as GB at 600. Then manipulate your BC in the solver until it gives you your observed hit data at 800 , or even better 1000. Slight nudge to the middle BC digit is all it takes.

Once this is done, your solver is now extremely reliable data , based on actual hits, with somewhat of a custom drag curve.

Hi Marc - Hope you are dong well.

yeah...one of the limits I found with 4DOF (versus the classic BC based solver they include in the 4DOF app) is that they don't give you access to BC if you use the a bullet with drag curve from their library.

And @Ledzep recently clarified that axial form factor is not really intended for truing as we seem to commonly think about but rather to compensate for bullet yaw from a specific barrel (or that's what my very small mind understood).

"Axial Form Factor is an adjustment that is made barrel-to-barrel, and even muzzle device to muzzle device to adjust for the muzzle exit yaw state that causes down-range drag effects."

This post and the one immediately after.

Is the Hornady 4 DOF's only use as a comedic tool?

Maybe it's me, but this is the magic 8 ball of ballistic calculators. I really like the set up, but as for it's predictions... Well I might as well just guess. Wish I knew what I was doing wrong.

www.snipershide.com

I do note that Hornady changed the axial form factor adjustment and it now takes you an explanation/tools/tables for different methods of how to determine its value. I'm not sure I want to mess with it at all, frankly.

 

[Ledzep]

Hi Marc - Hope you are dong well.

yeah...one of the limits I found with 4DOF (versus the classic BC based solver they include in the 4DOF app) is that they don't give you access to BC if you use the a bullet with drag curve from their library.

And @Ledzep recently clarified that axial form factor is not really intended for truing as we seem to commonly think about but rather to compensate for bullet yaw from a specific barrel (or that's what my very small mind understood).

"Axial Form Factor is an adjustment that is made barrel-to-barrel, and even muzzle device to muzzle device to adjust for the muzzle exit yaw state that causes down-range drag effects."

This post and the one immediately after.

Is the Hornady 4 DOF's only use as a comedic tool?

Maybe it's me, but this is the magic 8 ball of ballistic calculators. I really like the set up, but as for it's predictions... Well I might as well just guess. Wish I knew what I was doing wrong.

www.snipershide.com

I do note that Hornady changed the axial form factor adjustment and it now takes you an explanation/tools/tables for different methods of how to determine its value. I'm not sure I want to mess with it at all, frankly.

What you're doing with Axial Form Factor in 4DoF under the hood is shifting the Cd values in the Cd vs Mach curves up or down in 1% increments. In our testing we found that to be a more accurate representation of what is happening between barrels, powders, muzzle devices etc. when the net drag varies.

When you change the BC in a 3DoF/BC-based solver, it slants the reference Cd vs Mach curve of the standard projectile. You're effectively taking a ratio of Cd along the Mach axis. The fundamental flaw with G1/G7 based solvers is that you're using Cd vs. Mach data from a projectile that isn't the projectile you're shooting and trying to use BC as a scalar to get close enough that it works for your purposes. With 4DoF, you're using Cd vs. Mach data along with physical properties of the specific projectile you're shooting. The Cd vs Mach curve of your bullet may scale nicely with the G1 or G7 standard, or it may have many places along the Mach regime that do not agree well, and selecting a single BC value is a compromised approach to "fitting the curve". Both lying to the app about MV and selecting a single BC value is a great way to have the app work in 1 set of conditions, but trend wrong in other conditions/locations. It's because you're feeding it potentially (and to varying degrees) wrong Cd values, as well as lying about the Mach regime (MV) to get your trajectory to line up.

To clear this up a little bit better, one of the methods we use (when the opportunity arises) because we have access to the Doppler head is to take our match rifles and loads along on days that we're doing doppler testing. At any time, before I zero, after, it doesn't matter... I can use the Doppler head as a very expensive chronograph and get EXACT MV, but more importantly I can also capture down-range velocity at 400-800yd. I can then go into my 4DoF file, update environmental data, set the MV and select the bullet I'm shooting, then use the table to show me down-range velocity. I will then move AFF up or down to match my say 600yd velocity to the doppler data. At that point, there is an almost perfect drag representation of what my rifle is doing with that bullet and I almost never touch it after that. Also-- worth noting-- when we do that, we've almost never seen a setup that needed outside of 0.94-1.06. So purely using MV and doppler down-range data I can square away the velocity and drag portions of the file 100%. Then it's up to me to input accurate scope over bore and zero angle/range. That 4DoF file at that point is bulletproof. You are matching very closely both the starting point (MV/Mach) and the drag data, then have the sighting system correlated.

As I said in the other thread, we limit the amount of allowable play with AFF because 99% of the time you should be between 0.95 and 1.05. If you are doing something that requires you to go to the limits or near the limits, it's often a great indication that something else isn't right. Scope over bore, MV (which can shift day to day with temp, humidity of powder, etc..), lighting conditions and zero wander, scope tracking, etc... Outside of an app bug we're extremely confident in the velocity/drag portion of the app being EXCEPTIONALLY accurate.

 

[ScPiper]

What you're doing with Axial Form Factor in 4DoF under the hood is shifting the Cd values in the Cd vs Mach curves up or down in 1% increments. In our testing we found that to be a more accurate representation of what is happening between barrels, powders, muzzle devices etc. when the net drag varies.

When you change the BC in a 3DoF/BC-based solver, it slants the reference Cd vs Mach curve of the standard projectile. You're effectively taking a ratio of Cd along the Mach axis. The fundamental flaw with G1/G7 based solvers is that you're using Cd vs. Mach data from a projectile that isn't the projectile you're shooting and trying to use BC as a scalar to get close enough that it works for your purposes. With 4DoF, you're using Cd vs. Mach data along with physical properties of the specific projectile you're shooting. The Cd vs Mach curve of your bullet may scale nicely with the G1 or G7 standard, or it may have many places along the Mach regime that do not agree well, and selecting a single BC value is a compromised approach to "fitting the curve". Both lying to the app about MV and selecting a single BC value is a great way to have the app work in 1 set of conditions, but trend wrong in other conditions/locations. It's because you're feeding it potentially (and to varying degrees) wrong Cd values, as well as lying about the Mach regime (MV) to get your trajectory to line up.

To clear this up a little bit better, one of the methods we use (when the opportunity arises) because we have access to the Doppler head is to take our match rifles and loads along on days that we're doing doppler testing. At any time, before I zero, after, it doesn't matter... I can use the Doppler head as a very expensive chronograph and get EXACT MV, but more importantly I can also capture down-range velocity at 400-800yd. I can then go into my 4DoF file, update environmental data, set the MV and select the bullet I'm shooting, then use the table to show me down-range velocity. I will then move AFF up or down to match my say 600yd velocity to the doppler data. At that point, there is an almost perfect drag representation of what my rifle is doing with that bullet and I almost never touch it after that. Also-- worth noting-- when we do that, we've almost never seen a setup that needed outside of 0.94-1.06. So purely using MV and doppler down-range data I can square away the velocity and drag portions of the file 100%. Then it's up to me to input accurate scope over bore and zero angle/range. That 4DoF file at that point is bulletproof. You are matching very closely both the starting point (MV/Mach) and the drag data, then have the sighting system correlated.

As I said in the other thread, we limit the amount of allowable play with AFF because 99% of the time you should be between 0.95 and 1.05. If you are doing something that requires you to go to the limits or near the limits, it's often a great indication that something else isn't right. Scope over bore, MV (which can shift day to day with temp, humidity of powder, etc..), lighting conditions and zero wander, scope tracking, etc... Outside of an app bug we're extremely confident in the velocity/drag portion of the app being EXCEPTIONALLY accurate.

How accurate can the 4Dof be if it does not have the exact bullet I am using in the library? For example, I am using the 6.5mm Berger AR-hybrid OTM 130gr bullet which is not in the 4Dof library. Could this potentially look like a scope tracking issue after 800yds in the ballistic calculator, where there is an obvious difference between mils recommended and what is actually needed?

 

[Ledzep]

How accurate can the 4Dof be if it does not have the exact bullet I am using in the library? For example, I am using the 6.5mm Berger AR-hybrid OTM 130gr bullet which is not in the 4Dof library. Could this potentially look like a scope tracking issue after 800yds in the ballistic calculator, where there is an obvious difference between mils recommended and what is actually needed?

You're not using the 4DoF portion of the app if you're not selecting a bullet from the library.

The app also has a 3DoF/BC portion that is more or less the same as most other G1/G7 solvers with some small tweaks.

 

[ScPiper]

You're not using the 4DoF portion of the app if you're not selecting a bullet from the library.

The app also has a 3DoF/BC portion that is more or less the same as most other G1/G7 solvers with some small tweaks.

I forgot to put in the above post that I had selected the Berger 130gr VLD Target as that was the one I thought would be the closest to the AR-Hybrid OTM.

 

[Ledzep]

I forgot to put in the above post that I had selected the Berger 130gr VLD Target as that was the one I thought would be the closest to the AR-Hybrid OTM.

Doing it wrong, unfortunately. There are specific dynamic responses to the oncoming airflow that are predicted with 4DoF and changing internal/external dimensions (i.e. using a different bullet) is enough to cause meaningful differences in outputs, let alone the blanket differences you'll see in the Cd vs. Mach performance between the two bullets.

In short, it doesn't work that way and nobody can vouch for any accuracy problems you (are very likely to) encounter. I'd bet you have better luck using legacy solvers or the BC side of the Hornady ballistics app until we get that bullet in the library. If you want to donate and send in 50-100 bullets attn: Jacob Morrow to Hornady Mfg. (3625 W Old Potash Hwy, Grand Island NE 68803) we will eventually get them in the library.

 

[ScPiper]

Doing it wrong, unfortunately. There are specific dynamic responses to the oncoming airflow that are predicted with 4DoF and changing internal/external dimensions (i.e. using a different bullet) is enough to cause meaningful differences in outputs, let alone the blanket differences you'll see in the Cd vs. Mach performance between the two bullets.

In short, it doesn't work that way and nobody can vouch for any accuracy problems you (are very likely to) encounter. I'd bet you have better luck using legacy solvers or the BC side of the Hornady ballistics app until we get that bullet in the library. If you want to donate and send in 50-100 bullets attn: Jacob Morrow to Hornady Mfg. (3625 W Old Potash Hwy, Grand Island NE 68803) we will eventually get them in the library.

I just might do that, I have about half a box or maybe more that I am not using that I could send up there for y'all to mess with.

 

[Fig]

IMO a solver is only good for getting you in the neighborhood/on the steel. I've never populated a solver with information, including everything out of the Kestrel, and had it smack center of target with zero truing and 1 round down range. I don't know anyone who has. It could have fifty more inputs and probably wouldn't be any more accurate.

The people who win matches are the ones who put a lot of rounds downrange and have real DOPE from many different conditions, and their data isn't generated from a solver, but from recording impacts. How many times have you gotten a wind hold from your Kestrel and not believed it, held where you think it's more likely to be by "feel"/"intuition"/whatever, and been right? How many times have you gone to the zero range before the match and had a huge shift when the solver didn't predict much based on atmospherics? I'll bet I'm not alone at all.

The thing about the phone hits home. I need to write more in the book with the Rite in The Rain pages and look at my phone less. I've gotten somewhat lazy, but then I've been shooting a lot of NRL22, which sort of makes makes it easier to be more lazy.

For $5 I will certainly give it a shot, and will attend a class if you come within striking distance of middle America.
Just like the weaponized math, I think this is kewl.

 

[Baron23]

What you're doing with Axial Form Factor in 4DoF under the hood is shifting the Cd values in the Cd vs Mach curves up or down in 1% increments. In our testing we found that to be a more accurate representation of what is happening between barrels, powders, muzzle devices etc. when the net drag varies.

When you change the BC in a 3DoF/BC-based solver, it slants the reference Cd vs Mach curve of the standard projectile. You're effectively taking a ratio of Cd along the Mach axis. The fundamental flaw with G1/G7 based solvers is that you're using Cd vs. Mach data from a projectile that isn't the projectile you're shooting and trying to use BC as a scalar to get close enough that it works for your purposes. With 4DoF, you're using Cd vs. Mach data along with physical properties of the specific projectile you're shooting. The Cd vs Mach curve of your bullet may scale nicely with the G1 or G7 standard, or it may have many places along the Mach regime that do not agree well, and selecting a single BC value is a compromised approach to "fitting the curve". Both lying to the app about MV and selecting a single BC value is a great way to have the app work in 1 set of conditions, but trend wrong in other conditions/locations. It's because you're feeding it potentially (and to varying degrees) wrong Cd values, as well as lying about the Mach regime (MV) to get your trajectory to line up.

To clear this up a little bit better, one of the methods we use (when the opportunity arises) because we have access to the Doppler head is to take our match rifles and loads along on days that we're doing doppler testing. At any time, before I zero, after, it doesn't matter... I can use the Doppler head as a very expensive chronograph and get EXACT MV, but more importantly I can also capture down-range velocity at 400-800yd. I can then go into my 4DoF file, update environmental data, set the MV and select the bullet I'm shooting, then use the table to show me down-range velocity. I will then move AFF up or down to match my say 600yd velocity to the doppler data. At that point, there is an almost perfect drag representation of what my rifle is doing with that bullet and I almost never touch it after that. Also-- worth noting-- when we do that, we've almost never seen a setup that needed outside of 0.94-1.06. So purely using MV and doppler down-range data I can square away the velocity and drag portions of the file 100%. Then it's up to me to input accurate scope over bore and zero angle/range. That 4DoF file at that point is bulletproof. You are matching very closely both the starting point (MV/Mach) and the drag data, then have the sighting system correlated.

As I said in the other thread, we limit the amount of allowable play with AFF because 99% of the time you should be between 0.95 and 1.05. If you are doing something that requires you to go to the limits or near the limits, it's often a great indication that something else isn't right. Scope over bore, MV (which can shift day to day with temp, humidity of powder, etc..), lighting conditions and zero wander, scope tracking, etc... Outside of an app bug we're extremely confident in the velocity/drag portion of the app being EXCEPTIONALLY accurate.

Thanks @Ledzep I'd like to caution us all that this is Marc's Gravity Ballistics thread and we sort of went way off topic here.

I'll say this then bow out of Marc's thread....as you know, most all of us don't have access to a $150-200 K Doppler system to get dead nuts velocity at 600 yards...or really any significant range.

I do see where Hornady has added tools and instruction to adjust AFF based on POI delta from POA and I can do that at 547 yards (500 meters).

I have done this and adjusted MV to true to results seen on the target at that range. I was 4" high consistently with actual MV so I increased MV until come up in app matched actual needed on target.

My plan is to clone this gun in 4DOF, set MV to actual (with Garmin), and then go into AFF....actually my "Total Come Up" should work or just use "Impact Location". Be interesting to see how that plays out.

P.S. - edited and I don't know how I frak'd up typing "Total Come Up" as one of the approaches in 4DOF app. sigh....just getting old and had my "MV Trued" gun in the app on my mind.

Cheers and thanks