G7 for BC for .308 Noslers?

[andrewctillman]

I am fine tuning some range cards.

Does anyone have the G7 data for 168 and 175 grain CC bullets?

Also would like the 165 -168 grain BT or AB if it is published.

I am shooting a little bit flatter than I anticipated at Horse Ridge using the G1 even when I account for altitude and angle.

Thanks.

 

[257 Ackley]

Go to this site; http://www.jbmballistics.com/cgi-bin/jb ... mp-5.1.cgi and use the library for the bullets in question to get your come-ups.

 

[andrewctillman]

Thanks 257,

I went to JMB who I had used previously to make a range card and when I clicked on the library link for the Nosler and then selected the G7 rather than G1, the BC did not change from .5 to whatever it would be in G7 (something less than .3 I would think).

I have got pretty good results from JMB using G1 at .490 rather than .505 since the average of G1 BC for the 175 Sierra is around that for the 175.

Do you suppose this just means the library does not have a G7 for the Nosler?

PS I loved the 257 class rifles and used a 257 Weatherby for many years and later a 25-06.

 

[257 Ackley]

It doesn't change for me on the other bullets either. If I have the right bullet showing in the library, it will usually give me spot-on numbers. I have found it is important to make sure your line of sight section has the correct number input. The measurement from the center of the bore to the center of the scope is your sight height. Check that out on your rifle.

 

[andrewctillman]

Thanks 257,

Since I have a 30mm tube on my scope it is probably not exactly 1.5 inches.

I did not think to correct for that.

Thanks!

 

[Guy Miner]

I have got pretty good results from JMB using G1 at .490 rather than .505 since the average of G1 BC for the 175 Sierra is around that for the 175.

Do you suppose this just means the library does not have a G7 for the Nosler?

The Sierra Matchking and the Nosler Custom Competition are so doggone close in the .30 cal 155's and 168's that I've seen no difference in my "come ups" out to 600 yards. I've got to believe that they've got very close to the same actual BC.

FWIW, Guy

 

[andrewctillman]

I did recalculate drop using both 1.625 and 1.75 which appears to be closer to accurate for a 30mm tube and high rings.

It made surprisingly little difference. About 1/2 MOA at 1,000 yards. But that is where you need to be most precise (5 inches difference in drop).

I could easily have written that off to the BC being inaccurate when it was just the rings.