Re: Correct Form Factor to use
Outside of word of mouth, the only way to know which drag model(ratio) fits best is through testing. If Brian says G7 works better, I tend to believe him.
Keep in mind though, you need to use different BCs for different drag models to produce the proper ratio and resultant drop calcs. FF is Cd for your bullet divided by Cd from a test bullet at any given Mach#. In this case, the G7 test bullet.. So you must enter G7 BC for your bullet to compare, if using G7 drag as a basis.
A 'starting point' for this is: G7BC = G1BC / 2.027176 That should get ya close.
Now keep in mind that local BC is different than std BC due to atmospheric conditions. So don't ignore these on entry of your field results for comparison.