drag factor in software question

[rickp]

Hey guys,
I've been using Exbal ballistic software and it doesn't have drag factor setting like G1 G2 G3 etc...
A couple of days ago a bought iSnipe ballistic software for the Ipiod touch. This software does have a drag factor option in it.
To compare software and results I entered the same info in both devices, however on the ipod I used G1 as the drag factor. The results I got were almost identical.

Now here is my issue. My understanding is G7 is the more accurate drag factor for a .308 175gr Sierra Matching King. When I used G7 in the Ipod, the results I got were almost a whole MOA difference at 400 yards from the results I got using G1.

The difference in numbers is not my question, different settings will give me different numbers, my question is does anyone know what drag factor Exbal uses? and
Do I really need to use G7, I've only ever really used G1.

1 MOA is quite a difference.

Thanks
R.

[taliv]

haven't used exbal, but i would assume they're using 'published' numbers, which are almost always G1.

My experience is that using the "litz" selection in jbm (online) and in the bulletflight program (iphone) are much better predictors of dope than any G1 BC I've used.

I believe the Litz numbers are G7. I further believe they are measured, not calculated based on the profile and weight of the bullet. Whether it is more accurate because it's G7 or measured, I can't speculate.

I think you have to buy his book to get the actual number, as it is hidden in both calculators.


eta: per your followon question on the hide, the G1 BCs are only "accurate" at a given velocity. So rather than do calculus, they just essentially say "over x fps, use BC of a. between y and x, use BC of b. between z and y, use BC of c." So you will enter multiple BCs in and get fairly close.

[MechEng]

It uses G1