Bryan,
Thanks for stepping in and helping resolve this issue. I'm sure you didn't have the time to read all my posts on this topic, which has lead you to the misconception that I'm promoting G1 over G7. I assure you that's not the case. I'll summarize my position.
If a manufacturer is going to publish a single BC value for a given bullet, be it G7 or G1, my understanding of Ken's contention from his July 2007 Shooting Times article is that the best method to calculate BC is to measure the velocity near the muzzle and then the TOF over a long distance.
To test that contention without having shareable raw data to work with, I assume that either Berger's published G7 BC or Sierra's multiple G1 BC values more closely match their bullet's real retardation than the published G1 BC. That assumption is based on the fact that the shape of these VLD bullets is more similar to the G7 standard projectile, or that multiple G1 BC values compensate for the shape of the G1 standard projectile.
If Ken's method results in a more accurate BC value than the method currently being used, then a calculated equal TOF G1 BC relative to the G7 BC (or multiple G1 BCs) should also be more accurate than the published G1 BC.
Before starting this topic I opened the "Determining a Load's Maximum Range" topic where the consensus was that a load's maximum range is where remaining velocity drops to Mach 1.2. The few claims of accurate shots into the sub-sonic velocity range often got the BS card played. I understand there are exceptions, as in anything, but manufacturers should publish BC values that best represent their bullets for how shooters will most often use them.
I've posted downrange data for several bullets showing the equal TOF G1 BC better matches the published G7 BC than the published G1 BC does. My conclusion from such comparisons is that Ken's method would result in a better G1 BC value as well as a better G7 BC value if applied to the raw shooting data. Better as in predicting trajectory more accurately for how most shooters will use a given bullet.
What's really being compared are the methods for calculating BC from raw shooting data. That is, what's the accuracy of average BC values for several velocity ranges (velocity zone BC averaging) as compared to allowing nature to average BC values over an infinite number of velocity ranges by using TOF. If BC values represented a linear rate of change in retardation from velocity zone to velocity zone, then the velocity zone BC averaging method would produce the same results as using the TOF.
However, the rate of change in retardation is not linear with respect to BC across different velocity zones. For the G7 standard bullet with a BC of 1.000, and relative to Mach 2.23 the retardation is 1.414 times less at Mach 1.79 and 1.326 times more at Mach 2.68. Thus, averaging the BC values in these ranges doesn't accurately represent the true retardation from Mach 2.68 to 1.79 as each zone is being given equal weight. Rather than using complex methods to correct for non-linear retardation, simply using TOF over a long range allows nature to perfectly average the BC values.
I'm aware of Lapua using Doppler radar and have already talked about some of the problems with that method on this topic if it's done outdoors. Assuming they collect perfect data for a given bullet, they still have to fit it to the G7 standard to calculate the G7 BC. If they use velocity zone BC averaging to make that fit they will introduce the same errors as before. If they use TOF over a long range, they'll get a better BC value, but in measuring TOF, Doppler radar is no more accurate than other far less expensive methods.
The Military uses Doppler radar, but they don't try to fit the data to a given standard projectile, the actual bullet is the standard. It seems Lapua did the same thing and incorporated their radar data into their ballistics program. Only then is Doppler radar data better than BC methods of calclating down range values. That is, as soon as you fit the radar data to a standard bullet by converting it to a single BC value you lose all the data that doesn�t fit the drag profile of the standard bullet.
I assume Lapua used radar data in their ballistics program as they weren't publishing BC values for some of the bullets listed in their exterior ballistics program. When I used the output of their ballistics program to calculate an equal TOF BC, there was little difference in downrange data between their program as compared to another program when using that equal TOF BC value, which was surprising. Either there's no real accuracy advantage or they were really converting the radar data to a single BC within their program in order to work with existing algorithms. I might cover that in a future topic.
As for your book, I find it very useful and as another member reminded me, it's about the only independent source of BC data covering several manufacturers. I know your second edition is out and I intend to order a copy as soon as next year's budget is approved.
