Home Forums Hunting & Shooting Long Range Hunting Help needed- Math Guys - G7 Approximation time

Applied Ballistics for Long Range Shooting by Brian Litz.

Appendix A11 Formula 19.1 is supposed to allow me to approximate the G7 BC for Bullet in Hand but BC not supplied.

I have a strong hunch that it should fall Just Shirt of the Standard ( 1.036 Form Factor), but darn If I can get into the ballpark.

Someone willing to enter into a transalantic Excel / Standard / metric Formula Check ?

Thx in advance.

In on the first page....

Not Sure, what you are saying...

in my Phone right now, so breaviated Here.

And Limited, by spell Check it appears. Capitals all haywire as Well.

I will Check in via Desktop once able.

Ok, here now a bit more comprehensive -

Cartridge .308 Win.
Rifle Savage 10 PH 20" Barrel
Suppressor ASE Utra Jet Z - Compact
Bullet LOS HT 140 grains - no BC supplied

Near velocity: 868 m/s (SD 8.4 m/s)
Far velocity: 780 m/s (0,58 m/s for only three shots)
Chronograph Pro Chrony

JBM calculates a G7 BC for these numbers of 0,152.

Just for giggles - I want to use the Litz - Formula to calculate this bullet and see if I can get close. So far no such luck. I do not seem to be able to get it right.

The formula you find attached.

Oh, come on now; not all at once, please...

Why not go shoot it and figure things out?

Say, thats an idea...

Its whats next on the agenda to take it to 300 and 600 m.

Still, and I am appearently alone in this, I like to think it worthwhile, to approximate G7 BC for bullets with such not supplied (most, actually), to get into the ballpark.

Do you have a g1?

In order to calculate without a bullet to measure, someone has to provide values for B, C, D, E, and F.

What are your near and far distances for those velocity measurements? Can't calculate b.c. without that. Atmospheric data measured at the same time as the velocity readings is necessary as well (temp, pressure, altitude, etc, or density altitude).

Good luck measuring a bullet accurately enough to get a meaningful result from that formula. If you're a machinist or other occupation with specialized measurment tools, maybe, otherwise it'll be entertainment only and not accurate enough.

Yonder, thanks.

Near Distance 5 m; far distance 95 m; so distance between 90 m.

This really is only for entertainment.

Highbean, not, unfortunatly, no BC supplied (G1 nor G7). Hence my antics.

Thanks, I will send this along.

You still need the atmospheric data as well, and it needed to be measured at about the same time as your velocity readings.

Once you have that, start plugging numbers into a ballistic calculator until you find a b.c. value that matches those velocity readings.

Like Higbean and Yondering have said: (1) go shoot said bullet, (2) obtain bullet drop data, (3) backcalculate the G7.

That HT design doesn't look very aerodynamic to me.