Quote Originally Posted by mapper View Post
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.