G1 vs G7 Drag For Long Range Bullets

[LongRangeMike]

I've got the rifle and scope setup for some long distance shooting and I'm getting ready to start 1000+ yard shooting. So I just started taking my crono / bullet data looking to get some solid ballistic data.

Here is what through me off, I was wanting to test the accuracy of some of the ballistic tools I've gathered (Excel one from this website and online ones such as Hornady). Using the online Hornady one I couldn't believe the difference when using G1 vs G7 and wanted to know what those of you in these forums use.

Using the G1 function my bullets would have ~384 ft/lbs of force at 1750 (~1 mile) but with G7 it's well over 1100 ft/lbs of force and the drop difference is significant.

What say you if you have experience at this range?

FYI
3740 FPS, 180 Grain .475 B/C - 1.5" Sight Above the Barrel, 200 Yard Zero

 

[JackinSD]

Quick question: What did you use for your G7 BC?

Here is a little information on the differences of the G1 and G7 BC.

http://bulletin.accurateshooter.com/2012/02/g1-vs-g7-ballistic-coefficients-what-you-need-to-know/

 

[Broz]

If you are using the same number (the .475) for both a G1 and a G7 profile that is incorrect. The .475 would be a G1 rating for a 180 I would guess, but you need the G7 BC number for that bullet to use a G7 model.

Jeff

 

[LongRangeMike]

Quick question: What did you use for your G7 BC?

Here is a little information on the differences of the G1 and G7 BC.

G1 vs. G7 Ballistic Coefficients — What You Need to Know « Daily Bulletin

Thanks for the link but I'm a little more lost now because I'm not sure if Nosler references to G1 or G7.
I use the same B/C for both... might be the issue. I use 165 and 180 grain Nosler BST. I got the BST from the Nosler website on the bullets. And correction my Velocities were for the 165, not the 180.
B/C for 165 Grain is .475 for the BST Spitzer
B/C for 180 Grain is .507 ''....
Ballistic Tip - Nosler - Bullets, Ammunition, Rifles, Brass, Reloading Data, Hunting, Shooting, Reloading, Load Data
Not sure if those are referenced to G1 or G7... But need to know.

 

[Broz]

Not sure if those are referenced to G1 or G7... But need to know.

Looks like G1 Bc's to me

Jeff

 

[LongRangeMike]

Thanks, I asked Nosler through their website so we'll see what they say. But using the same B/C will yield crazy results. Bullets in my gun are expensive even when reloaded so I want to at least be close at long ranges so I can make adjustments with fewer rounds fired.

Thanks

 

[JackinSD]

Sorry Mike. Wasn't trying to confuse you.

The point I was trying to get across, as I knew your problem, was that you were using the G1 BC for both.

 

[Beng]

Hi Mike
Buy "Applied Ballistics for Longrange Shooting" from Bryan Litz and read it.
All Problems solved after that.

 

[Joe King]

Thanks for the link but I'm a little more lost now because I'm not sure if Nosler references to G1 or G7.
I use the same B/C for both... might be the issue. I use 165 and 180 grain Nosler BST. I got the BST from the Nosler website on the bullets. And correction my Velocities were for the 165, not the 180.
B/C for 165 Grain is .475 for the BST Spitzer
B/C for 180 Grain is .507 ''....
Ballistic Tip - Nosler - Bullets, Ammunition, Rifles, Brass, Reloading Data, Hunting, Shooting, Reloading, Load Data
Not sure if those are referenced to G1 or G7... But need to know.

your G7 BC's are
165 - .227
180 - .241

G7 will give you more accurate results, to get a good drop using G1 BC's with SBT bullets of any kind you need to to model several velocities and tie them together. The more you get into VLD type bullets the more G1 will be off.

 

[LongRangeMike]

Joe & Others,

Thanks for the clarification and getting the G7's for me. Nosler got back to me today and suggested I use the JBM ballistics calculators to convert their G1 values to G7 especially at yardages 800+.

Now I'm much more clear on G7 vs G1 just need to put it into practice!

 

[gebhardt02]

The G7 standard more closely resembles modern bullets (pointy tips and boat tails) than the G1 standard and thus the drag curves are a better match. You can get the job done with the G1 BC's but as Joe King said, you'll want to utilize the different BC's for stepped velocity boundaries. If you have a program that'll accept G7's, then you can basically just use that one number as provided above. Given the choice between the two BC values, the G7 is a better model. If you are stuck using the G1's, it'll work best to set it up with the different BC's for different velocities. And I second the recommendationon Litz's book, I have it sitting in front of me right now. Good luck.

Geb