Since I believe you'd rather recite the entire text of War and Peace than do any of the simple calculations which I told you to do and which prove you wrong, I have done the important one for you. Using the bullet you chose, using the exact same assumptions you used, using the exact same methodology you used, when launched at 2500 fps that bullet has an average G1 BC of .548 from the muzzle to Mach 1.2.
It is very clear to anybody who can read, that you were wrong. The large difference was caused not by Berger's methodology, but by your choice of a very high muzzle velocity and the fundamental fact that one G1 number will only be correct at one velocity for this bullet. By now, this should be painfully obvious to everybody and I suspect, had you understood it in the first place, you never would have started this thread.
It's no secret that if you pick a different MV the equal TOF BC may come out different. The real question is, is my original G1 BC a better value for this bullet than Berger's published G1 BC over a wide range of MV? If so, then my point about there being a better technique for calculating BCs is correct. Here are the numbers.
![[Linked Image]](http://farm6.static.flickr.com/5143/5844148978_78eb27cd63_b.jpg)
As you can see for a MV of 3000 fps the equal TOF G1 BC is more accurate as compared to the G7 BC than Berger's published G1 BC is out to 1300 yards even though velocity drops to 1.2 Mach at 1150 yards. For a MV of 2500 fps the TOF G1 BC is more accurate out to 700 yards and actually to 850 yards where the velocity drops to Mach 1.2. This is more evidence that the equal TOF technique is better for calculating BC values in the velocity range these VLD bullets will be used by most long range shooters.
That said, I made reference in my original post that Berger's number showed they were concerned with predicting their bullet's performance in the subsonic range. The numbers above demonstrate that as well.
The number Berger uses is actually very close to this value. This value is the one that will be closer for the vast majority of users for that bullet. For the few shooting 378's necked down to 6mm, your value will be closer.
That no single G1 value works for all applications with this bullet is most obviously not a fault of Berger's methodology. It's due to the fact the bullet follows a different curve.
That is all. Case closed. You started the thread for nothing. You were wrong. I know that is painful to admit (maybe try and prove yourself right using the Pejsa method now?) but it would be for the best.
For all your blustering you've only shown that my original post is correct even when extended down to a MV of 2500 fps.
What in the hell are you doing using multiple BC values? Your first post, the reason you started this thread, was not to declare how accurate Sierra's stepped BC method was. Quite the contrary. It may help confuse the issue so you can sweep the important stuff under the rug, but the rug can be lifted.
The only reason I used a Sierra bullet is because you asked for one as an example. Forget it and go back to the 115 Berger (or any other closely following the G7 curve) that you chose and the methodology you were advocating in the beginning of the thread.
I picked it because you offered the SMK as a counter example even taking the time to list out the multiple BC values. Using the bullet you picked I again demonstrated that the equal TOF value produces a more accurate G7 BC value than the one Bryan and JBM calculate using their velocity zone averaging technique.
Now you want to go back to the 115 Berger, which I did above and once again demonstrated that my original G1 BC is better even at the 2500 f/s MV.
You didn't start this thread to prove using multiple G1 BC's could give you accurate results. It is quite revealing that your final number-crunching comparison to prove you are correct did not contain the methodology you started the thread advocating as the best. That's a concession without saying it outloud.
No, but you offered up the SMK as a counter example. Neither of us has the original firing data for that bullet, so the only valid comparison for my G7 BC and the one Bryan and JBM calculate is Sierra's own BC values. What were you thinking would be the reference when you listed the multiple BC values?
Again, more gibberish to cover up ballistics errors. You claimed a more accurate ballistics method. I have demonstrated it is less accurate.
You've said that a difference of 5.8 inches at 1500 yards is a significant error, but I'm not advocating using the equal TOF G1 BC in place of the Berger's G7 BC. The point is that the equal TOF G1 BC more accurately matches the G7 BC than Berger's published G1 BC. If you want to claim 5.8 inches is significant then the 21.8 inches from Bergers G1 BC is 3.7 times bigger difference. You call that less accurate?
Isn't it nice how things work out so well when you can simply make up data? From what basis do you �guess� the above? Again, your first claim word for word:
Go look at Bryan's data points for the two bullets. You'll see the 115 Berger has a much wider velocity spread and more data points. The "guess" as you call it is based on understanding variability and confidence levels.
I gave you an example to illustrate your misunderstanding, a bullet with a i7 of near 1 and an i1 of near 0.5 that happens to follow the G1 curve better than the G7. And your response is if Bryan had kept shooting longer he would have gotten the opposite results? Very weak.
Just so there's no question later as to which bullet you now offer up, here's what you wrote before
�the Sierra 107 Matchking has an average I7 of 0.993�should be a �perfect match,� eh? Wrong. It has over seven times the variation the Nosler has. It's actually a much better fit to the G1 curve than it is the G7 curve (even though its G1 I of 0.508 is quite a ways off from the �perfect� 1.0).� The Nosler you were referring is the Nosler 95 Partition.
We can use Sierra's multiple BC values to see if their .243 107 grain Matchking better follows the G7 or, as you claim, the G1 curve. No need to use JBM as it doesn't support multiple BC values and my prior post shows the program I'm using gets nearly the same values as JBM does.
The G1 BC values are 0.527 down to 2500 fps, 0.522 down to 1800 fps, 0.509 down to 1600 fps, and 0.495 below 1600 fps. Obviously, Sierra doesn't think their bullet matches G1 well or they wouldn't need to publish four BC values for it, but let's continue and see what the data says.
I'm going to use 3500 fps and take the data out far enough to get into the subsonic range to see which of Bryan's BC values best matches Sierra's own multiple BC. That way we get into velocities were there's a difference between G1 an G7 outside the profile convergence velocity zone. Bryan give this bullet a G7 BC of 0.262 and a G1 BC of 0.510. Here's the data out to 2000 yards.
![[Linked Image]](http://farm4.static.flickr.com/3225/5845017949_88dcf65b9b_z.jpg)
Your contention that this bullet better match G1 than G7 is wrong. If you look at Bryan's data for this bullet you'll see that he has only 6 data points. Remember what I was saying about getting a different result with more data points, well this is a classic example. Also, most of Bryan's data is within the drag profile convergence velocity range where the G1 and G7 are indistinguishable. There's also a flaw in the way Bryan calculates Variation.
Like Bryan said, this bullet shouldn't mach the G1 standard better than the G7 standard, and it doesn't. The Form Factor theory is proven correct. If you weren't so busy trying to teach maybe you could learn something.
If you have any other bullets you want to offer as counter examples please do the work of posting the actual downrange numbers. It will save me time debunking your contentions.
