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G1 or G7

 
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  #8  
Old 04-10-2012, 12:36 AM
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Re: G1 or G7

No Max, G1 & G7 are calculated the same as [sect density / Form factor], and form factor is [your bullet's drag Coef / a standard bullet's drag Coef] throughout the velocity range.
The different results here(with G7) are due to different 'standard bullet drag Coef' applied.

The closer you get to [apples / standard apples], the better the results.
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  #9  
Old 04-10-2012, 04:22 AM
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Re: G1 or G7

I think for shooters that are only shooting out to 700-800 yards, it doesn't make a whole lot of difference as long as they are using accurate G1orG7 data. I have used the G7 and G1 inputs with my 6.5x284 using 140 VLD's. My drops are essentially identical out to 800 yards in both actual drop data in the field, as well as with the output generated from my ballistic calculator. Until I get out to 800 yards or so, the G7 formula then begins to show less than a one click difference in elevation to at least 1000. This is less than 3" difference at 1000 yards. Beyond this range the difference increases. This is also visually apparent when looking at the ballistic curves in Bryan's book. Once the velocities fall much below 1800 FPS, the difference in drop data occurs with the G7 form factor. I'm working on a 338 Lapua that I will use at +1000 yards. Using the G7 data will make a more substantial difference in developing accurate drops at those extended ranges. Bryan's book is very useful since he has developed good G1 and G7 data for most of the bullets available.
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  #10  
Old 04-10-2012, 03:11 PM
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Re: G1 or G7

Quote:
Originally Posted by Mikecr View Post
No Max, G1 & G7 are calculated the same as [sect density / Form factor], and form factor is [your bullet's drag Coef / a standard bullet's drag Coef] throughout the velocity range.
The different results here(with G7) are due to different 'standard bullet drag Coef' applied.

The closer you get to [apples / standard apples], the better the results.

I'm not sure what I was thinking. With SD factored out, it would be the FF. It is the "standard" compared to that is different. Got it.
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  #11  
Old 04-10-2012, 08:14 PM
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Re: G1 or G7

Also, don't forget that the G1 BC is the correct BC to use for shorter, flat based bullets (at all ranges), like many varmint bullets.
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