Ballistic Coeficient G1 or G7

scsims

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I just downloaded the Shooter program for my phone and didn't know if I should use the G1 or G7 BC. I'm shooting a .308 168gr SMK. The G7 seems closer to what I've seen in the field shooting, G1 seems to be about 1.5 MOA off.

How do I know which to use?
 
The G7 is usually closer at the longer distances. I feel either will work for your 308 if you have solid velocity input along with accurate field conditions. Watch shooting too close to the chronograph. I keep em 18' from the muzzle so the blast does not interfear. Also remember many cheaper chrono's will lie. I would use the G7 and check the drops at 300, 500, 700 and 1000 on the same day and range if possible. Then use the velocity that puts them all spot on to .25 moa average from center group.

Jeff
 
G7. I dont want to take business away from Eric over at Berger Bullets, but he has a book with an entire chapter explaining what i am about to cover.

If your bullet looks like a Flat Base say 55gn V-Max bullet (.22) you should use G1.
If your bullet has a Boat Tail then use G7.

The G1 is not Bad it just does not model a Long range Projectile as closely as the g7. I believe a 6mm Lapua Scenar bullet is a close resemblence to the G7 Standard Projectile.

I would highly reccomend picking up his book. Costs $50 and is worth ever penny. HUGE hard cover book filled with information. If it was a college text book it would be $400... That is how nice it is.
 
I have experienced no difference between the two using my 6.5x284 with 140 VLDs out to 1000 yards. My ballistic calculator shows about a 1-2" difference in elevation at 900 yards and this appears consistent with actual impact points. I haven't tested past 1000 yards, but my calculator begins to show more significant differences, with less correction using G7. The ballistic curves in Bryan's book appears to bear this out as well.
 
Now that I have all the correct info in the program, it looks like G7 has 9.4 MOA @ 500 and G1 has 11.2 MOA.

So actually G1 is closer to what I'm seeing. I guess I just use which is closer and adjust my MV to make the program match field results??
 
Now that I have all the correct info in the program, it looks like G7 has 9.4 MOA @ 500 and G1 has 11.2 MOA.

So actually G1 is closer to what I'm seeing. I guess I just use which is closer and adjust my MV to make the program match field results??

There is no way they should be that different. You have something else wrong in one of those bullet models.

At 500 yards you should see a very small or no difference at all.

I suggest you go over your input data , you have something throwing one off.

Jeff
 
I find it hard to believe after reading most of his book that with a boat tail bullet you will get more consistent results with G1. I would be willing to bet that you are not inputting the correct items.

If you think about it, use the model that looks like your bullet, G1 looks like a Pistol FMJ bullet, whereas the G7 looks like a Lapua Scenar.

Check your inputs.
 
according to bryan litz
168 smk g7 is .218 g1 is .427


the nosler 165 balistic tip
g7 .227
g1 .444

use the G7 that i have given you, they were tested by Mr. Litz himself rather than computer generated.

Those were Average BC's from 1500 - 3000 fps i believe. That will get you VERY close on almost ANY shooting situation. If you need more precision id reccomend buying his book and it has all that information in it.


I feel bad giving any more information that that, as the guy worked hard on the book and provides it for dirt cheap.
 
according to bryan litz
168 smk g7 is .218 g1 is .427


the nosler 165 balistic tip
g7 .227
g1 .444

use the G7 that i have given you, they were tested by Mr. Litz himself rather than computer generated.

Those were Average BC's from 1500 - 3000 fps i believe. That will get you VERY close on almost ANY shooting situation. If you need more precision id reccomend buying his book and it has all that information in it.


I feel bad giving any more information that that, as the guy worked hard on the book and provides it for dirt cheap.

Brian states in his book that the 168SMK has an inherent stability issue at ranges greater than 700 yards or so. It is a design flaw with of the bullet. Also, the Ballistic tip, due to the short boat tail, may behave more like a G1 then a G7. I use this 165gr. bullet in my 308 at 2800 fps and get very accurate trajectory results using G1.
 
Just to clarify above I have never shot either of these bullets, and maybe have shot 5 30 cal rounds in my life :)

Just took it from the book, shout of said above that i have no experience with either of these bullets (or the caliber for a matter of fact :p)
 
My brother just bought a kestrel 4500 with a trac .. it just uses a g1 bc .. no input for a g7.. spot on at 550yards and 750 but i had to adjust my fps a littel bit.
 
I was wondering the same thing. I was playing with shooter on my phone and with data for my 338 edge, using the g1 it says come up 25.1 and the g7 says 21.1. Any help?
 
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