Ballistic Coefficients

[Jackthebear]

Why is there a discrepancy between Bc’s from AB and Hornady? I shoot the the 143 ELD-X and Hornady has the G7 listed at .315. Conversely, AB has it in their library at .292! Can someone chime in on this?

 

[Formidilosus]

Why is there a discrepancy between Bc’s from AB and Hornady? I shoot the the 143 ELD-X and Hornady has the G7 listed at .315. Conversely, AB has it in their library at .292! Can someone chime in on this?

First Hornady lists BC for Mach 2.25. Second, AB chronically lists ELD-M and X BC’s low.

 

[Lou270]

ABs (and Bergers) are averaged from 3000-1500 fps. I think Hornadies are to 800 yards which could be much less than where a bullet crosses 1500 fps. They also publish by mach number and if I remember their lowest mach number was still above 1900 fps. I don’t know if explains all the difference but the AB/Berger approach is more conservative so their numbers will be lower. Sierras to me is most frustrating. They list at different velocities but there is no consistency in how they do it so nothing is apples to apples.

Lou

 

[Muley Buck]

First Hornady lists BC for Mach 2.25. Second, AB chronically lists ELD-M and X BC’s low.

Why do they differ and who's math is right then?

 

[Formidilosus]

Why do they differ and who's math is right then?

Everyone I know has to use Hornady’s data when they true to make it work with ELD-M and X’s.

 

[Gribley]

Do you trust the hornady bc with the 105 BTHP?

 

[wind gypsy]

Hornady lists the 143 eldx G7 as 0.294 @ mach 1.75.

 

[JGRaider]

Not sure I'd trust BC's published by the company that brought us the melting bullet tip dramatics. Don't trust covtard Steve Hornady either. I'd take Litz's AB numbers and go from there. He wrote the book on ballistics. YMMV.

 

[parshal]

Published BC numbers are just a starting point to use to verify your dope if you're using a ballistics app that only uses BC. AB using an average BC they gather from doppler. I can't speak for exactly what Hornady does but the above posts seem about right to me.

If using the 4DOF app you'd use form factor to dial in the dope (for a Hornady bullet) rather than a published BC.

If using an AB app, you'd probably use a CDM or PDM. If not, you're changing the muzzle velocity and/or the BC to get the dope to match what you see on target.

 

[wind gypsy]

Using AB curves rather than a bc # seems to work real well most of the time for me. I imagine one could use 4DOF similarly? The published #'s I really only use for bench racing ballistics rather than actual firing solutions.

 

[Formidilosus]

Published BC numbers are just a starting point to use to verify your dope if you're using a ballistics app that only uses BC. AB using an average BC they gather from doppler. I can't speak for exactly what Hornady does

The they are using Doppler radar. Hornady’s BC’s are correct at the stated Mach. Mach 2.25 and Mach 2.0 work just fine for the terminal range of ELD-M and ELD-X. People need to stop listening to nonsense and believing that small differences in G1 BC are even noticeable or measurable in the field at mid long range (800’ish yards).


Almost no one should be adjusting the BC in an app unless they have a Doppler radar or a Oehler 89. Without that, there is no way one can detect a .005 G1 BC difference. You are changing something that you can’t measure or actually know is the cause and it will lead to issues. In the terminal
Image of bullets, use good Doppler radar derived BC’s and adjust MV. Any errors noticed at 800-1,000 yards (or farther) is due to MV, initial zero, loss of zero, or scope adjustment errors.


Here’s the 103gr ELD-X at 800 yards:

.512 G1 BC (Mach 2.25). 4.4 mils for elevation.



.498 G1 BC (Mach 1.75). The same 4.4 mils for elevation.




Good G1 BC’s absolutely result in the same data to max terminal range as G7 BC, CDM’s, 4DOF, etc.

This stuff is pole vaulting over mouse turds.

Using AB curves rather than a bc # seems to work real well most of the time for me. I imagine one could use 4DOF similarly? The published #'s I really only use for bench racing ballistics than actual firing solutions.

4DOF works the same as CDM