B.C. Values Honest or Dishonest?

[TheDavidKemp]

Hey guys, new to the sport more than just shooting M24s/M110s out to 1000 and I'm researching some new bullets for a 6.5 creed that I have. Looking into Hornady 140/143/147 Berger 130/140/156 and other one offs. With the knowledge and information coming from AB, I assume the Berger G1/G7 numbers are accurate. The Hornady values seem to blow away the other companies. So my question is, are companies like hornady, sierra and nosler being honest or are they inflating their findings?

Thanks

 

[TxWelder35]

I know my 136gr Lapaua scenars L are conservative on their G1 BC. I believe they list .545 but in order to for my ballistic calculator to match my down range results I needed to change it to .6

 

[Steel head]

I think they’re fairly accurate now for a general guideline.
It also depends on what distances your using them at.
1000 yards and in I’ve found all the common bullets I’ve used BC’s to be easily close enough.
After 1200 all of them need adjustments even Hornandy’s 1.75 Mach numbers.

 

[TheDavidKemp]

thanks guys for the responses. I guess I just assumed Hornady/nosler were a little dishonest with their numbers seeing as they're so much higher than berger for some of the perspective weight classes. I guess I was being naive' in assuming the bergers were so much better than others but wondering why they were lower values at the same time.

 

[Supersubes]

Hornady got their own Doppler setup a few years ago for actually measuring BC’s. I find their Bc’s to be dang close to perfect. Go to their website and look at the eld page. They actually give the BC’s in velocity bands. What’s printed on the bullet box is from the fast (mach 2.25) band.

I think their prices are more impressive than the Bc’s.

 

[Lowlight]

BC numbers are fluid, dynamic in fact and will change from system to system, rifle to rifle.

 

[frank320]

on the same BC values note, a quick question:
As an example using 6.5 PRC 147 ELD-M, Hornady has 3 BC bands:
Mach 2.25 = 0.351 G2
Mach 2.0 = 0.332 G2
Mach 1.75 = 0.321 G2

What is the correct way to use these values for a bullet starting at Mach 2.5 and ending at, say Mach 1.9?

Here are a few ways to calculate:
1) As bullet drops from Mach 2.5 to Mach 2.1, use 0.351 G2, then as bullet drops from Mach 2.0 to Mach 1.9, use 0.332 G2
or
2) Since ending velocity is Mach 1.9, just use 0.332 G2 across the whole range from Mach 2.5 to Mach 1.9
or
3) Use linear interpolation each step along the way to average out the BC from Mach 2.5 down to Mach 1.9 using both 0.351 G2 and 0.332 G2

Thanks.

 

[TheDavidKemp]

Appreciate everything.

I have to change the way I think about these things. Using the numbers given as a reference. I'm trying to decide which weight class bullet to go with, 130/140/147/153-156.

Shooting a 26" krieger in 6.5 creed and wanting to stay around that 2850 line because I do use this rifle as a hunting rifle for eastern whitetail and western big game so carried energy is important.

Whats better: pushing a 130 to 2900+ or a ride a slow 156 and get what I can? Im basically trying to get a grasp on what numbers I can actually get from a 130 or 156.

 

[Steel head]

on the same BC values note, a quick question:
As an example using 6.5 PRC 147 ELD-M, Hornady has 3 BC bands:
Mach 2.25 = 0.351 G2
Mach 2.0 = 0.332 G2
Mach 1.75 = 0.321 G2

What is the correct way to use these values for a bullet starting at Mach 2.5 and ending at, say Mach 1.9?

Here are a few ways to calculate:
1) As bullet drops from Mach 2.5 to Mach 2.1, use 0.351 G2, then as bullet drops from Mach 2.0 to Mach 1.9, use 0.332 G2
or
2) Since ending velocity is Mach 1.9, just use 0.332 G2 across the whole range from Mach 2.5 to Mach 1.9
or
3) Use linear interpolation each step along the way to average out the BC from Mach 2.5 down to Mach 1.9 using both 0.351 G2 and 0.332 G2

Thanks.

I used the 1.75 Mach value to 1200ish comfortably.


The other Mach values are for closer targets.

I made a custom BC using all three but it didn’t jive to actuals as well as a straight 1.75 Mach BC.

To get it to true to a mile I’m using a .308 BC with a slight FPS tweak.

It’s not perfect but it’s close enough.

 

[frank320]

As a further example, StrelokPro has a multi-BC input function. I really wonder the various ballistic apps takes into proper account how Hornady uses these BC bands, or how it should be used to properly calculate a correct BC value. Because back to the OP's question, if we are inputting or using these BC bands incorrectly at various distances, or if the app is not using these BC bands correctly, we have only ourselves to blame when the trajectories don't line up - i.e the BC data from manufacturers might be correct, but they are specific to a particular band/range, and we need to input the correct BC value and do the proper calculation for the range that we are shooting at.

 

[Steel head]

As a further example, StrelokPro has a multi-BC input function. I really wonder the various ballistic apps takes into proper account how Hornady uses these BC bands, or how it should be used to properly calculate a correct BC value. Because back to the OP's question, if we are inputting or using these BC bands incorrectly at various distances, or if the app is not using these BC bands correctly, we have only ourselves to blame when the trajectories don't line up.

I’m sure I could sit down and hash out a custom BC on ballistic AE or AB for my bullet and barrel combinations I tried 4dof and with a bit of fiddling with the form factor it’s almost perfect.
Poof.

I’d rather be shooting, reloading or looking at porn than fiddling with numbers for an hour or two.

Now I just dream about a ballistic AE app with 4dof built in.

 

[Rob01]

Hornady got their own Doppler setup a few years ago for actually measuring BC’s. I find their Bc’s to be dang close to perfect. Go to their website and look at the eld page. They actually give the BC’s in velocity bands. What’s printed on the bullet box is from the fast (mach 2.25) band.

I think their prices are more impressive than the Bc’s.

Yup and if you use the 4Dof with the custom curves there is no need to even worry about the BC. Been using 4Dof all year and it's very accurate. I haven't had to mess with anything. Put in the info and it's on.

 

[TheDavidKemp]

I know every other post someone is asking "what should I get/use" .... fill in the blank, but it sounds like the most advantageous method would be for me to choose a bullet (preferably hornady) with heaviest possible weight and still get the speed I want and follow this while using Hornady calculator.
I'm not asking to be told what to do, I just want to have information laid out in a manner I can understand and make my own decision. But I feel like I'm on the brink or past the point of splitting hairs.

Thanks again everyone for input and clarification.

 

[Lowlight]

Since BCs are velocity dependent, you definitely have to balance the weight vs the speed, heaviest is not always the best based off barrel length and velocity.

So try to balance both so they work out in your favor,

 

[308pirate]

I feel like I'm on the brink or past the point of splitting hairs..

You are.

Go shoot. The bullet tells the truth.

 

[Steel head]

Go shoot. The bullet tells the truth.

This!

 

[DownhillFromHere]

Well, to go slightly astray with this thread... As @frank320 noted, Strelok Pro supports multi-BC inputs, which I would assume would map to the velocity-related BC "bands" as reported by Hornady and other bullet sources.

But I haven't been able to find any documentation on how to do this. 'Twould be nice to know.

 

[Greg Langelius *]

Been offline/off range since December due to health. I had started a load development for the 260/143ELD-X/H-4350, and intend to pick it back up this Fall. I suspect it'll be particularly good, especially at my medium altitude of 4350ft ASL.

I found pressure early, so I'd strongly suggest starting fairly low and working on up with this particular bullet; I suspect the longer bearing surface is involved. There were other issues with the rifle (I.e. short headspace), and the solution still needs to be proven; but everything is precisely correct by the gauges/numbers now. All of my 260 and 308 dies and chambers are set up to coincide with the same 308 case gauge and headspace gauge; SAAMI all the way.

Greg