MacLorry,
Thank you for your analysis of the G1 vs G7 BC based trajectories. I have responses to several of your statements.
I agree that the method described by Ken Oehler (deriving a G1 BC over long range based on tof) is the best way to derive a G1 BC, if you have to use a G1 BC. It's also the best way to derive a G7 BC. Since most modern projectiles are shaped more like the G7 standard, the G7 BC is a better representation of the bullets Mach dependent drag characteristics than G1. In other words, there is a 'best practice' for using the poor G1 standard, but it's still a poor standard. Granted the error between G1 and G7 is small, but it's still error, so why would you choose to use it when the G7 BC is known?
Regarding predicted remaining velocity. You're correct that the G1 BC, if derived from tof data, will produce inaccurate estimates of remaining velocity. You argue that it's not important to you and that's fine. It is important to some who are using hunting bullets with known terminal velocity performance thresholds. So again, you're not arguing that G1 is better, just that this particular downside is not important to you.
I will point out that Berger is not the only major bullet company who's adopted the use of G7 BC's. Earlier this year, Lapua began offering G7 BC's for their bullets as well:
http://www.lapua.com/en/products/reloadingI'll remind you that Lapua has tested all their bullets under radar and has a very accurate picture of each bullet's supersonic drag characteristics and has decided to represent them with G7 BC's. In other words, don't just take my word for it.
Aside from predicting trajectories, don't forget about the smoke and mirrors games that are possible when advertising different G1 BC's. A company can advertise an inflated G1 BC for a bullet that's technically 'accurate', but only at high velocity and of no use for predicting long range trajectories. The adaptation of G7 BC's cuts down on these kinds of uncertainties that add up to missed targets.
I will acknowledge that for most bullets, in most of the supersonic range of flight, the G7 vs G1 based trajectories are very similar (assuming you've averaged the G1 BC for just the right velocity range). But I ask, why would you knowingly choose to incur a small amount of error with G1 BC's when G7 BC's will allow for predictions with less error?
I'll close by saying that since my book has been available which provides accurately measured G7 BC's, the general trend has been overwhelmingly positive. I see and get a lot of good feedback from shooters who are using G7 BC's to hit targets with far greater regularity at far greater ranges than ever before. The fact that you might be able to get close with a G1 BC is one of the reasons why the paradigm shift towards a better (more representative) standard will take time, but I believe that the merits of G7 BC's are strong enough that the paradigm will continue to shift.
Take care,
-Bryan
