G1/G7 ballistic coefficient diffrences

[seadog]

And mapper, when I rest up and get sober,i'd like to continue this conversation.

[mapper]

Found this...about diffrent models..

http://www.sportingshootermag.com.au...c-coefficients

http://www.frfrogspad.com/extbal.htm

Sounds good.....pause button engaged.

[Arclight]

Come on Arclight I know you can correct me at some point.

For what reason would I correct you?

[seadog]

Because im thinking you know a lot more than I do about this subject.

[Airgator0470]

So,
To do a table right,
If a person had a list of g7 bc's at diffrent velocities, would they take an average of them, or use the one at the velocity/longest range they intend to shoot, providing the velocity is still supersonic,( mach 1.2 I think I saw somewhere) then verify by shots on targets at known ranges? Or put whatever bc is given either g1 or g7, and a measured muzzle velocity, and adjust from there, or are the diffrences not enough to be concerned with at NRA mid to long range distances...
I don't have anything capable of reaching farther than that..

Jbm ballistics has the g7 data in their library listed as (litz) otherwise it is g1 I think...
The bullet data base has some listed with velocities but does not make a distinction of which model it Is..

It may be a moot point with my shooting skills,or lack of, but I would like to know the proper way to derive a drop/driftc chart based on best available info..

Other wise I have been within reason and a couple clicks with a measured muzzle velocity, and a simple bc.. but that has been at short ranges

Charles... I think you're making this more difficult than necessary... just start with either G1 or G7 at the muzzle and do the field work to fine tune.

Regardless of whether your initial chart is derived from using G1 or G7 BC's... you STILL will need to verify the end data AT THE RANGE. I've used G1 data for YEARS and in the past couple, G7... both are adequate to get close... and both require in the field data verification and fine tuning.

This thread reminds me of the debate years ago between a guy on Sniper's Hide and Brian Litz... lots of back and forth if I recall.

The best way to build a drop chart is to START at a given point... shoot to verify and fine tune, and then discover what YOUR rifle does with YOUR loads.

I don't have the data handy and can't find it... but I've seen charts developed with G1 data and G7 data and neither was significantly more precise than the other. It's the IN THE FIELD shooting and verification that matters in the end.

[mapper]

Bob,
I agree... it wasn't untill I saw the chart in the 2nd link I posted that showed the diffrences between them was not much..they both agreed with each other from 0- 600 yds then were within reason of each other further out..

I just never saw that before... so yes the diffrences are there, but not enough to be concerned with, as field data rules. And either one will get close enough.

[Airgator0470]

Bob,
I agree... it wasn't untill I saw the chart in the 2nd link I posted that showed the diffrences between them was not much..they both agreed with each other from 0- 600 yds then were within reason of each other further out..

I just never saw that before... so yes the diffrences are there, but not enough to be concerned with, as field data rules. And either one will get close enough.

One good thing about the shoot in April, is we will have the ability to get out past 500... the only problem is I'd like to shoot 10 rounds at 600, 700, 800, 90 and 1K and then go to the target and actually measure what's going on. A hit at those distances is simply "a hit"... unless you see where on the target the bullet struck, which is hard after the first 20 minutes of open range, you have little idea if it was a solid COM hit or a barely on the target hit... to me that's MOST IMPORTANT.

[Jafar]

Not to discredit anyone in this thread, because I have learned from reading it, but TRex has some great videos about this very subject on his YouTube channel.

[Airgator0470]

Not to discredit anyone in this thread, because I have learned from reading it, but TRex has some great videos about this very subject on his YouTube channel.

I love watching most of those videos...

[Airgator0470]

https://www.youtube.com/watch?v=gjzs79kDr6E