how to interpret new BC's

recent trend in several projectile manufacturers is to publish multiple values for BC (G1 & G7) based on velocity.
eg Hornady now publishes “200 yard” Mach 2.25 (2,512 fps @ ICAO Standard Atmosphere**) G1 and G7 Ballistic Coefficient (BC) numbers for all A-TIP, ELD-X, and ELD Match bullets. Mach 2.0 (2,233 fps @ ICAO Standard Atmosphere) and Mach 1.75 (1,954 fps .
And state " values at Mach 1.75 (1954 fps @ ICAO Standard Atmosphere), should be used when calculating trajectories for shooting beyond 600 yds."

My question is for calculating long range eg 1000 yards, have Hornady already used an average of the 3 values and time in flight to come up with the Mach 1.75 value ?
or should you derive an average yourself based on
x% at Mach 2.25 + Y% @ Mach 2.0 + Z% @ Mach 1.75 ?

@chainsaw, it is a pandora's box :thumbsup:

a lot of this is just marketing hype, trying to justify publishing higher BC values than a competitor, or defending low values against inflated ones.

In my experience Berger has a fairly good take on BC values. Litz has done a ton of work, and is not afraid to publish and put data in the public domain.

Here is an interesting article on their website: https://bergerbullets.com/nobsbc/var...with-velocity/

At the end of the day, whatever is on the box or on the website, is just marketing to me. Use that as a guide, but you need to shoot actual drops at distance to verify and get real-world values that work for you.

I have used the Litz G7 values published in his book for projectiles of various manufacturers, and found them to be extremely accurate out to silly distances. If you want the Nth degree of info, have a look at the custom drag curves for Applied Ballistics. @andyanimal31 on here is a huge fan those and has had good results with them

The only bc figure i trust is the bc figue i get from the Applied Ballistics app, which come from Brians dopler testing, not just manufacturers marketing figures.

Yep, agreed and use Litz data when ever I can get it. But is this data available for some of the newer pills? Especially the newer ELDMs and X’s?

Strelok Pro has a place you can put in multiple BC values.
My take is that trajectory isn't very sensitive to small changes in BC at medium ranges so no ones noticed it much till now and it very hard to measure BC at a specific Mach. Except for Brian Litz.

Different algorithms in apps. Hornady 4dof calculates different to AB. The Kestrel has the ability to bend the custom drag model. In std apps use the G7 if shooting past 1000. You can true your BC in your app to your rifle. Remember the advertised BC is for certain speeds so if you have a short barrel and or slow twist your BC may not be optimised so therefore you may need to lower the number to get your ballistic curve to match. With the 338 in Ballistic arc I used to run the normal BC to 1600m then change to the lower BC through transonic and out to 2km.