G7 vs G1

[CharlieNC]

I understand the logic for using G7 calculations, especially for long-range. When looking at a number of cases for a range of bullet weights and calibers (.220 - .338) it is interesting to see there is a PERFECT correlation between the G7 and G1 BC values (see attached plot)???? So it looks like the measurements do not distinguish anything differently, since if you know G1 then you can easily calculate G7. Am I missing something?

 

[afrench]

G7 is approximately 0.512 x G1.

or, G1 approximates G7 / .512.

must use the correct velocity bands for G1 for any accuracy.

this is discussed in Litz's book, Applied Ballistics for LR Shooting.

 

[Bryan Litz Ballistics]

The reason you're seeing such a consistent relation between G1 and G7 (the factor of .512), is because they're all averaged for the same speed range (3000 to 1500 fps).

If you look at the G1 vs. G7 BC at different speeds, you'll see they're not always related by a factor of .512, because they both change differently with velocity. The G7 drag curve being more representative of modern long range bullets.

-Bryan