Range Report Which Ballistic Coefficient Should I Use? (Hornady ELDM)

[FourT6and2]

I see that Hornady lists different G7 figures for the same bullet depending on if you look at the "ammo" page or the "bullet" page. This is for 6.5 Creedmoor 140gr ELD-M. I've been using a G7 of 0.312 ever since the ammo was released. But now the ammo page shows 0.305 and the bullet page shows 0.326.

WTF.

So what do I use? And why do they list two different G7 coefficients for the same bullet?

 

[Rocketvapor]

I would think this one;
6.5mm 140 gr. ELD Match

Mach 2.250 .646 G1 0.326 G7

Mach 2.0 0.637 G1 0.320 G7

Mach 1.75 0.616 G1 0.310 G7
Going ELR? maybe that's where the .305 comes from.

 

[FourT6and2]

I would think this one;
6.5mm 140 gr. ELD Match

Mach 2.250 .646 G1 0.326 G7

Mach 2.0 0.637 G1 0.320 G7

Mach 1.75 0.616 G1 0.310 G7
Going ELR? maybe that's where the .305 comes from.

I'm shooting primarily from 100 - 1,000 yards. I think the 0.312 G7 I've been using has worked out pretty well. But I was gathering data on a new rifle today and noticed the G7 has changed and they list those three now. So... which one should I be using in TRASOL? Or should I just use .312 and then do a correction once I get out and shoot each distance? Or... should I use an average of all three or what?

 

[b6graham]

use which ever one matches the DOPE from YOUR rifle

these are just starting points

 

[Deleted member 10043]

Seems like we had a similar thread not too long ago. I would get it straightened out with Hornady. All you are going to get is dipshit answers from here that you already know.

 

[Redeye3]

Been shooting the 140s for little over 3 years in comps. I use 616g1 or .310g7. It has lined up thus far out to 1400yrds.

 

[Redeye3]

use which ever one matches the DOPE from YOUR rifle

these are just starting points

Kind of like guidelines??

 

[Sierra1wardog]

Velocity influences BC and I imagine the advertised bullet BC is probably towards the peak potential for marketing reasons. Maybe they had to bump the ammo BC down to match the advertised velocity?

 

[b6graham]

Velocity influences BC and I imagine the advertised bullet BC is probably towards the peak potential for marketing reasons. Maybe they had to bump the ammo BC down to match the advertised velocity?

Mach 2.250 .646 G1 0.326 G7

Mach 2.0 0.637 G1 0.320 G7

Mach 1.75 0.616 G1 0.310 G7

 

[FourT6and2]

Ok, so I guess I'll just start with what I've been using in my other rifle (0.312) and then correct for the actual drops at distance. In my other rifle, 0.312 has been pretty spot on out to 1200 yards.

 

[VegasHKShooter]

Or you could just go with Applied Ballistics CDM. They’re $1.99, and I have found every single one to be spot on out to 1000yds first round.
Just a suggestion.

 

[FourT6and2]

Or you could just go with Applied Ballistics CDM. They’re $1.99, and I have found every single one to be spot on out to 1000yds first round.
Just a suggestion.

Not quite sure what this is, but their website says they're only available for certain ballistic solvers/devices, none of which I have/use.

 

[Long Range 338]

If you get on Hornady website and do some digging they explain why they gave 2 different bc numbers. I believe the first bc was at 800 yards and the rest of the industry does them at 200 yards so they issued the 2nd bc for apples to apples comparison. The lower bc actually being more accurate IIRC

 

[VegasHKShooter]

Not quite sure what this is, but their website says they're only available for certain ballistic solvers/devices, none of which I have/use.

Should have made myself more clear.
If you use Applied Ballistics for your ballistic app, you can buy the Custom Drag Models for $1.99. They test certain bullets (TONS OF THEM) and will provide you with the info. It’s based off tons of real world testing, not just G1 and G7 BC’s. You input your parameters and it provides you with your drop info. They are EXTREMELY accurate. I use them for my 6.5CM ammo and my .308 ammo. I have gotten first round hits at 1000yds using the CDM’s.
The downside is you have to use Applied Ballistics as a solver. I use it and really dig it. If you use Ballistic AE, or something else, you don’t have access to them.

 

[Long Range 338]

Here is a good read from Hornady about BCs

https://www.hornady.com/team-hornady/ballistic-calculators/ballistic-resources/external-ballistics

 

[FourT6and2]

Should have made myself more clear.
If you use Applied Ballistics for your ballistic app, you can buy the Custom Drag Models for $1.99. They test certain bullets (TONS OF THEM) and will provide you with the info. It’s based off tons of real world testing, not just G1 and G7 BC’s. You input your parameters and it provides you with your drop info. They are EXTREMELY accurate. I use them for my 6.5CM ammo and my .308 ammo. I have gotten first round hits at 1000yds using the CDM’s.
The downside is you have to use Applied Ballistics as a solver. I use it and really dig it. If you use Ballistic AE, or something else, you don’t have access to them.

Ah, understood.

 

[Long Range 338]

If you get on Hornady website and do some digging they explain why they gave 2 different bc numbers. I believe the first bc was at 800 yards and the rest of the industry does them at 200 yards so they issued the 2nd bc for apples to apples comparison. The lower bc actually being more accurate IIRC

I finally located the Hornady's explanation on the different BCs for the ELD bullets. It is quite interesting how they posted lower BCs that averaged better and changed to the 200 yard BC later basically for marketing.

https://www.hornady.com/support/ballistic-coefficient

 

[davsco]

both hornady and sierra bullets give multiple bc values based on bullet velocity:

http://www.sierrabullets.com/documents/BallisticCoefficient-rifle.pdf
https://www.hornady.com/support/ballistic-coefficient

 

[FourT6and2]

Was able to get out at range the other day. Using G7 of 0.312 got me pretty bang on at 200, 300, 425, 500, 600, 800, and 900. Had to add in about 0.1 mil at each distance. This was with factory ammo, though. So it sometimes high, sometimes low.

At 1,000 something happened. Not sure what. But shots were all over the place. So that's still a mystery. Maybe the barrel got too hot and walked. I'm using a Bartlein Marksman contour. My other rifle, an M24, is solid. Barrel never moves from heat.

But as far as BC goes, 0.312 seems to be working for me.