I'm new to shooting the 6.5 creedmoor and have been using Hornady 6.5 CM 140 gr ELD match ammo. This ammo list two ballistic coefficients: G1 BC .646 and G7 BC .326. A real novice question but, which coefficient should I use ?
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Hornady 6.5 creedmoor ammo
- Thread starter Paul1262
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When you ask which coefficient you should use, what exactly do you mean? Will you be inputting this data into anything?
Most ballistic calculators that I have found require the BC to be included in the base information.
Gotcha!!!
In this case, that would be your G1 ballistic coefficient unless it specifically states otherwise.
Just a reminder though, whatever ballistics that ammo claims to have, it was acquired or done using Hornady's test rifle. In your particular rifle, that number may be somewhat different!
Hornady's standard ballistic calculator requires the ballistic coefficient however, their new 4DOF calculator does not. The new calculator is focuses more on projectile drag coefficient as opposed to ballistic coefficient data.
i thought, but as usual could be completely wrong, that g7 was better than g1, if your program takes both.
also, you want to put in stepped bc's if your program takes those, different bc's for different velocity bands.
www.hornady.com
also, you want to put in stepped bc's if your program takes those, different bc's for different velocity bands.
Ballistic Coefficient - Hornady Manufacturing, Inc
A-Tip®, ELD® Match, and ELD-X® Ballistic Coefficient Values Hornady originally published “800 yard”* average Ballistic Coefficient (BC) values for ELD-X and ELD Match bullets. This was done to provide the most usable BC from a trajectory prediction st...
I believe that you are correct about the G7.i thought, but as usual could be completely wrong, that g7 was better than g1, if your program takes both.
also, you want to put in stepped bc's if your program takes those, different bc's for different velocity bands.
Ballistic Coefficient - Hornady Manufacturing, Inc
A-Tip®, ELD® Match, and ELD-X® Ballistic Coefficient Values Hornady originally published “800 yard”* average Ballistic Coefficient (BC) values for ELD-X and ELD Match bullets. This was done to provide the most usable BC from a trajectory prediction st...
Regardless of which BC and calculator you use, you need to have an actual velocity. The test-barrel velocity printed on the box is almost never close enough to reality to be any more than ballpark useful.
So you need a chronograph. LabRadar or Magnetospeed are the most popular; take a couple of hours (or days) and read all the "which one is better" threads here. A $75 Caldwell optical unit is better than nothing. They work fine for what they cost: velocities are good but the units are quite a pita to set up and use.
The velocity data gets plugged into your calculator. I've played with a few different ones, including Hornady's 4DOF, but Strelok Pro remains my go-to. Ballistic data (BC, box velocity, physical characteristics, etc.) for Hornady 6.5CM 140-ELD can be loaded from the app's library of hundreds of factory rounds, then update the factory velocity with observed velocity. Enter weather data, and you're ready to go.
As an example of why I trust it: I recently took delivery on a new Vudoo .22. I tested and chronoed several kinds of .22 ammo, loading each from the Strelok library and updating the factory velocity with observed velocity from my LabRadar. I then "trued" data for the best one - with a 50-yard zero, I found the Strelok calculation for 300 yards was off by about half a mil. I entered the correction in the appropriate place. Then, just for fun, I got a 400-yard solution from Strelok and let fly at a 10" plate at that range. Two shots, two hits. Holdover from Strelok was over 21 mils - that's a bit over 25 FEET. At that range, the bullet is dropping about 2 inches per linear yard. And Strelok nailed it.
For both of my 6.5CMs, I never found truing to be necessary.
This goes way beyond your question of whether to use G1 or G7 BC; my point is, with any decent ballistic solver, the appropriate value is probably loaded from a library. IMO, an accurate (and consistent) velocity is the most important data point you need to find and load.
So you need a chronograph. LabRadar or Magnetospeed are the most popular; take a couple of hours (or days) and read all the "which one is better" threads here. A $75 Caldwell optical unit is better than nothing. They work fine for what they cost: velocities are good but the units are quite a pita to set up and use.
The velocity data gets plugged into your calculator. I've played with a few different ones, including Hornady's 4DOF, but Strelok Pro remains my go-to. Ballistic data (BC, box velocity, physical characteristics, etc.) for Hornady 6.5CM 140-ELD can be loaded from the app's library of hundreds of factory rounds, then update the factory velocity with observed velocity. Enter weather data, and you're ready to go.
As an example of why I trust it: I recently took delivery on a new Vudoo .22. I tested and chronoed several kinds of .22 ammo, loading each from the Strelok library and updating the factory velocity with observed velocity from my LabRadar. I then "trued" data for the best one - with a 50-yard zero, I found the Strelok calculation for 300 yards was off by about half a mil. I entered the correction in the appropriate place. Then, just for fun, I got a 400-yard solution from Strelok and let fly at a 10" plate at that range. Two shots, two hits. Holdover from Strelok was over 21 mils - that's a bit over 25 FEET. At that range, the bullet is dropping about 2 inches per linear yard. And Strelok nailed it.
For both of my 6.5CMs, I never found truing to be necessary.
This goes way beyond your question of whether to use G1 or G7 BC; my point is, with any decent ballistic solver, the appropriate value is probably loaded from a library. IMO, an accurate (and consistent) velocity is the most important data point you need to find and load.
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