Ballistic programs that dont agree

[BallisticsGuy]

For G1 calculations one has to understand that a G1 BC is really just a comparison to a reference projectile which has very well documented and known performance. Some poor schmucks had to go out and shoot huge numbers of rounds of reference projectiles in various conditions and come out with tables of results. Because of that a G1 BC being used on a non-G1 compliant projectile is really only valid to whatever distance it's meant to be valid to and outside of that it becomes rapidly less accurate. This is where BC "truing" (a tragically inaccurate term in this case) comes in and why it sucks. There are also methods to deal with this problem that involve BC banding and BC sloping which have the benefit of being more accurate but also more of a PITA for the layman.

FWIW, I would be very keen to find out how the math actually got implemented for 4DOF but I suspect that it comes down to is the same basic math we're familiar with but with custom drag tables created from a large amount of data gathering involving doppler radar.

 

[shawnb]

So, the output vs actual was very interesting.

-Range 1910yds
-Environment 28.12inhg, 40deg, 54.3/280deg
-wind 4mph from 3 oclock

AB- called 19.7 up 0.8 right
4DOF- called 18.8 up 0.7 right
Actual- 21 up 0.8 right

Returned to zero and was bang on after 1910 was shot.

I started playing with the AB and Hornady app. If i changed the AB from Litz custom curve and his G7 call of .386 to the hornady website advertised 0.362 for long shots, the drops match perfect. Same goes for the hornady app using the G7 calculator instead of the 4DOF.

Maybe the 4dof is dialed in for the updated design, and my original design doesnt work for it. I didnt even have enough room to adjust the axial form factor in the hornady app to come close. Adjusting it to 1.10form factor still only gets me to 20.74 mil not the 21 i needed.

As the days go on i will get more data points for different ranges and keep posting.

 

[Danehunter]

Yep, there are lots of rifle ballistics programs out there. Some like the original Horus program, are not as accurate as others like the Allied Ballistics engine or Hornady's Four Degrees of Freedom (4DOF).

Generally the less a ballistics programs relies on strictly mathematical models and more on real world input the better the results will be. Applied Ballistics uses Doppler radar for real world info. 4DOF uses information on the angle of the bullet's axis in relation to the trajectory as well as Doppler radar information.

Adding your rifle's info, such as accurate average muzzle velocities for a specific load, rifling twist rate, etc., will give the best results. But the environmental factors at the time of firing, such as those measured by Kestrel's latest 5700 weather meter with the Applied Ballistics engine must also be part of the Final Firing Solution. Listing those many factors here is pointless. Look them up on the Kestrel site for a full explanation.

If ballistics programs don't agree it is most likely because one or both do not take into account enough REAL WORLD information in making their predictions.

The admonition to "true" your rifle's trajectory on the range with the ballistic engine predictions should never be ignored. There will always be slight variations from the prediction due to barrel manufacturing variations, among other things.

Eric B.

 

[73driver]

I have found getting 2 diff apps to match is hard. My main experience is Shooter and AB. Yesterday I tried help a friend who bought Strelock Pro, I had AB, but I was able to manipulate numbers better in AB, we could find nowhere in Strelock to enter elevation, and it proved to be an issue.
You have a 1.4 mil variance in dope at 1780, a lot of vertical at that distance. If you are seeking advice, I would kick out your top calcs and rely on 4 DOF as it was designed for Hornady bullets, keeping AB as a solid backup. There comes a time when a guy just needs to launch a couple rds, visualize what happens and regroup. By regroup I mean manipulate inputs to match actuals. We have all struggled with an app, and always it is a box not checked, or too many checked, or a number off slightly, or the dreaded inflated bc numbers, which is becoming more scarce yearly.

I use a DA app and load that into my Strelock Pro. Who needs alt when it's DA that matters.

 

[milo-2]

I use a DA app and load that into my Strelock Pro. Who needs alt when it's DA that matters.

Right, we probably would have loaded DA in and ran off it, I scoured his app and could not find it, android.
I actually bought SP this am, found DA, not sure if it engaged, uninstalled it in 20 min and got a refund.
I shoot off a Kestrel 5700 with AB, I don't need apps, I keep one on the phone(AB) to help others, AB always works in a pinch, easy to use.
The Kestrel may be able to tell you DA in weather mode, but does not use it for calculations, it uses temp, pressure and humidity. We had those 3 parameters entered in Strelok Pro, did not help much, I guess SP is not for our kind, lol
I am not here to bad mouth Strelok, over my head.

 

[shawnb]

Same inputs on the website 4dof calculator as the app and completely different outputs. This one is pretty near bang on

 

[bigngreen]

I use a DA app and load that into my Strelock Pro. Who needs alt when it's DA that matters.

DA is a good quick solution but not as accurate a method.

 

[bigngreen]

We do live in an amazing time, I remember the only portable solution was Exbal, you had to be a banded BC tuning ninja to reach half as far as we do now with a quick download and it comes with an amazing BC library!! What fun!!

 

[73driver]

Right, we probably would have loaded DA in and ran off it, I scoured his app and could not find it, android.
I actually bought SP this am, found DA, not sure if it engaged, uninstalled it in 20 min and got a refund.
I shoot off a Kestrel 5700 with AB, I don't need apps, I keep one on the phone(AB) to help others, AB always works in a pinch, easy to use.
The Kestrel may be able to tell you DA in weather mode, but does not use it for calculations, it uses temp, pressure and humidity. We had those 3 parameters entered in Strelok Pro, did not help much, I guess SP is not for our kind, lol
I am not here to bad mouth Strelok, over my head.

Running my SP in IOS maybe explains some difference.

 

[73driver]

DA is a good quick solution but not as accurate a method.

Please explain. Temp, pressure and humidity are what get you Density Altitude.

 

[User4302021]

For G1 calculations one has to understand that a G1 BC is really just a comparison to a reference projectile which has very well documented and known performance. Some poor schmucks had to go out and shoot huge numbers of rounds of reference projectiles in various conditions and come out with tables of results. Because of that a G1 BC being used on a non-G1 compliant projectile is really only valid to whatever distance it's meant to be valid to and outside of that it becomes rapidly less accurate. This is where BC "truing" (a tragically inaccurate term in this case) comes in and why it sucks. There are also methods to deal with this problem that involve BC banding and BC sloping which have the benefit of being more accurate but also more of a PITA for the layman.

FWIW, I would be very keen to find out how the math actually got implemented for 4DOF but I suspect that it comes down to is the same basic math we're familiar with but with custom drag tables created from a large amount of data gathering involving doppler radar.

I have real suspicions of 4DOF.

It seems to work great for Hornady bullets, but I've not had good luck getting it to line up with Trasol, Strelok Pro, AB or Ballistic Arc using others bullets.

In the cases where it doesn't line up, it has been demonstrably wrong.

 

[User4302021]

Please explain. Temp, pressure and humidity are what get you Density Altitude.

The question, and therefore the potential for error, is where is the data you are using to calculate DA coming from?

Is it from conditions at your exact location? Or from some weather station somewhere else?

 

[Greyfox]

Having used most of the available APPS, given identical input, I have found they are all very close, at least in the supersonic region. At transonic, differences begin to show up with the AB due to algorithm treatment. Choice of APP for me really came down to the user interface and visibility. Since acquiring a Kestral 5700 I haven't bothered using an APP. Interestingly, using identical inputs the Kestral 5700 linked with the TerrapinX produces identical ballistic outputs as my Sig 2400, and Gunwerks G7 out to 1300 yards.

 

[Doug Herold]

What do you mean by this? I have been using Strelok Pro for 4 years now, you can input everything.

I have Strelok Pro, Trasol, AB, 4DOF, and Ballistic Arc.

I use them all to some extent, but Strelok Pro has been my favorite by far.

Mr. Rocket,
I too can not find where to input "elevation " in the Strelok. Where is it?