AB engine

JB.IC

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So several times I believe I’ve read in AB books that their AB engine accounts for increased SG which increases BC/Reduced Drag.

So I decided to try an experiment on three of my AB products: AB analytics, AB Elite, and AB Mobile.

I created a duplicate profiles where one gun was at an 8 twist with a SG >3 and one profile where the SG was <1 and everything else being the same.

The elevation out to 4K yards remained the same with a 0 wind value inputted.

I also checked to see aerodynamic jump with AB Mobile to see if SG would change elevation as AB books state increase in SG and a crosswind will cause elevation deflection. It did nothing out to 4K yards.

Anyone with AB software, would you kindly check your software and make adjustments for increased SG with zero wind and then check to see if aerodynamic jump is added when a full value cross wind is applied?
 
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rangerlong

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Using AB Analytics predicting the trajectory of an 185gr juggernaut
1:11 twist 10mph wind adds .11 mils of aerodynamic jump vs 0mph wind
1:8 twist 10mph wind adds .15 mils of aerodynamic jump vs 0mph

Not really sure if that's what you're asking. What does your AB Analytics show in that block when you add wind?

1577050345048.png
 

JB.IC

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“I also checked to see aerodynamic jump with AB Mobile to see if SG would change elevation as AB books state increase in SG and a crosswind will cause elevation deflection. It did nothing out to 4K yards.”

I’m only referring to aerodynamic jump not being computed for AB Mobile
 

JB.IC

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To further clarify, the AB books have claimed their engine is one of the only engines to factor in SG at different stability levels and when you go from a super low SG to a super high SG, the program doesn’t display any difference.
 

rangerlong

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It does work in AB Analytics so the engine itself does what the books say it does. It's possible they didn't implement that in AB mobile by design or by mistake. I don't have it to test.

Sounds like a question for @DocUSMCRetired
 

JB.IC

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Resting the AB Mobile fixed the Aerodynamic jump issue. AB Mobile is now computing different ADJ levels for different SGs when a full value crosswind is applied.

How ever none of the programs are factoring in different SG levels and its effect on BC. Going from a 30 twist with a SG of 0.16 to a 3 twist with a SG of 16.45 did nothing to the elevation at 4K yards.

I quickly scanned AB Modern Advancements in LR shooting; below is a picture of AB claiming it would take into account marginal stability.

37D65132-4817-4878-9D33-6CF1FC5A5020.jpeg
 
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rangerlong

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Ok, for this issue I can confirm that with changes in twist rate/stability elevation doesn't change whether I use the G7 BC or custom drag model.
 

JB.IC

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Ok, for this issue I can confirm that with changes in twist rate/stability elevation doesn't change whether I use the G7 BC or custom drag model.
Same here.

Here’s another mentioning I found

1EFB9545-6DDE-4BA2-A6A8-2C566C0EF673.jpeg
 

JB.IC

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It should change with twist rate, and bullet length. Not with BC. I am looking into this now as I tested it on AB Analytics and it worked properly. I will look into the apps next.
Doesn’t work for me and with the twist rates extremes I used, it should have worked beyond a reasonable doubt.

“ How ever none of the programs are factoring in different SG levels and its effect on BC. Going from a 30 twist with a SG of 0.16 to a 3 twist with a SG of 16.45 did nothing to the elevation at 4K yards.”

Programs produce zero elevation difference with the above difference in SG.
 

DocUSMCRetired

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Doesn’t work for me and with the twist rates extremes I used, it should have worked beyond a reasonable doubt.

“ How ever none of the programs are factoring in different SG levels and its effect on BC. Going from a 30 twist with a SG of 0.16 to a 3 twist with a SG of 16.45 did nothing to the elevation at 4K yards.”

Programs produce zero elevation difference with the above difference in SG.
We don't change the BC based on the SG. SG calculations are only accurate to +/- 0.1 and do have other nuisances. We are working on a more accurate way to account for this, and have already implemented it in some circles. Some of the applications and software do make changes.
 

JB.IC

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Programs produce zero elevation difference with the above difference in SG.
We don't change the BC based on the SG. SG calculations are only accurate to +/- 0.1 and do have other nuisances. We are working on a more accurate way to account for this, and have already implemented it in some circles. Some of the applications and software do make changes.
See above
 

Near miss

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Just tested, at least on Kestrel 5700 Aero jump finds its value from twist rate, as claimed in the book.

What I find interesting is how can one who uses cdm to lower the ballistic value because he is using a too slow twist? There is not much to play with.
 

DocUSMCRetired

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Just tested, at least on Kestrel 5700 Aero jump finds its value from twist rate, as claimed in the book.

What I find interesting is how can one who uses cdm to lower the ballistic value because he is using a too slow twist? There is not much to play with.

If you need to adjust the ballistics that is what DSF is for. DSF only calibrates a specific portion of the flight model, so as not to skew the entire model unnecessarily causing other issues.

The apps should be adjusting AJ for twist rate, and we are testing a new release of the iPhone app this week.
 

TriggerJerk!

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If you need to adjust the ballistics that is what DSF is for. DSF only calibrates a specific portion of the flight model, so as not to skew the entire model unnecessarily causing other issues.

The apps should be adjusting AJ for twist rate, and we are testing a new release of the iPhone app this week.
What is the ETA on the iPhone update Doc? And thank you for the info.