Are you thinking of BC the wrong way?

[Danehunter]

Brian,

Where (if at all) does Sectional Density enter the calculations in the Custom Drag Modelling?

Eric B.

 

[Danehunter]

Brian,

Where (if at all) does Sectional Density enter the calculations in the Custom Drag Modelling?

i.e. is SD a large factor in this calculation or merely incidental with no great effect other than resistance to side winds?

Eric B.

 

[Mikecr]

why have 5 zones for a bullet when you can have 30 or more using a CDM.

Hopefully we'll have a procedure/inputs to shape CDM curves for our bullets.
If I remember right, Pejsa had a retardation coefficient procedure that produced a single modifier input -field determined for each bullet. The attributes BC and RCoeff then stayed together as a pair.
Way ahead of his time.

 

[DocUSMCRetired]

Hopefully we'll have a procedure/inputs to shape CDM curves for our bullets.
If I remember right, Pejsa had a retardation coefficient procedure that produced a single modifier input -field determined for each bullet. The attributes BC and RCoeff then stayed together as a pair.
Way ahead of his time.

Ballistic Calibration has been a feature in AB from the start. The BC goes untouched and does get an adjustment value applied to it. Same thing works with the CDM. You don't modify the actual CDM, never have. You just apply a correction to it. You can see this in the DSF tables.

 

[THEIS]

Pejsa had a retardation coefficient procedure that produced a single modifier input -field determined for each bullet. The attributes BC and RCoeff then stayed together as a pair.
Way ahead of his time.

Hello,

Here is a lamens term recap of Pejsa's model, to include the retardation coefficient example.

Modeling Drag

THEIS

 

[THEIS]

You don't modify the actual CDM, never have. You just apply a correction to it. You can see this in the DSF tables.

Hello Doc,

What velocity range are you all going down to when building your CDMs?
Are you going into subsonic velocities when building your CDMs or are you staying supersonic?

THEIS

 

[DocUSMCRetired]

Hello Doc,

What velocity range are you all going down to when building your CDMs?
Are you going into subsonic velocities when building your CDMs or are you staying supersonic?

THEIS

We test them into subsonic.

 

[Longtooth32]

Our AB Android version is the last remaining hold out that allows for this. We are getting away from Segmented BCs and going to straight CDMs in all our programs/apps/devices. Segmented BCs in apps are essentially a Band-Aid fix. But why have 5 zones for a bullet when you can have 30 or more using a CDM.

Any plans on testing the .277 170gr Berger?

Thanks...

 

[DocUSMCRetired]

Any plans on testing the .277 170gr Berger?

Thanks...

Its already been tested and is in the CDM Library. I see it in the Kilo app, Kestrel App, and in AB Mobile. I just double checked.

 

[Longtooth32]

Its already been tested and is in the CDM Library. I see it in the Kilo app, Kestrel App, and in AB Mobile. I just double checked.

Thanks...I could not find the list of the included CDM bullet profiles.

So, I just go to the iTunes store, download the AB Mobile and the .277 170gr bullet profile will be on that app?

Thanks again...

 

[Tulsa Reiner]

So, where are the results of Applied Ballistics' testing/calculations available?

 

[chadd hughart]

Thank you Mr. Bryan Litz, as always, your posts are well appreciated !

 

[DocUSMCRetired]

So, where are the results of Applied Ballistics' testing/calculations available?

CDM data is not available to the public. The generic BC data is available through the Ballistic Performance of Rifle Bullets books. You can also find the G1 or G7 averaged BC in our app.

 

[graywolf]

To illustrate your point it would be really informative to show an example of a few different bullets where the measured/segmented CD data is superimposed on the G1 and G7 curves- depending on the bullet, the G7 or G1 (or neither) might fit well over a wide velocity range, right?