Thread: G7 BC's

Found this report the other day by accident. It might be of use to some of the Long Range shooters. Measured G7 BC's for Hornady, Sierra, Nosler, & Barnes projectiles.

Interesting article. Anyone brave enough to donate their chrony as the 200yd velocity measurement tool

Originally Posted by Tussock

It pains me just how hard some people suck at understanding what a ballistic coefficient actually is.

Tussock, is your comment in relation to this article, or something else ?

Originally Posted by ebf

Interesting article. Anyone brave enough to donate their chrony as the 200yd velocity measurement tool

NO

Just put it up there because it has Bryan Litz's Measured BC's listed. Bergers are absent but at least they put the G7 on the box label. Not sure the authors conversion to G1 using form factors is reliable, and I don't use G1 BC anyway.

Originally Posted by ebf

Interesting article. Anyone brave enough to donate their chrony as the 200yd velocity measurement tool

Can't see a problem with it but how will you read the numbers

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Loooooong lead for F1 master external display

I'm nervous enough about hitting the bloody chrony in it is 10ft away. Guess you could make up a nice armour plated box, coz the down range one is going to get dinged a couple of times...

Arnt G7 specific to boat tails??im just learning this shit.

The window is like 12 inch square at least..,I thought we could all shoot 1mm groups at 200

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yea but murphy reckons you "will" put your first round thru the chrony

Originally Posted by Neckshot

yea but murphy reckons you "will" put your first round thru the chrony

Yep. Been there done that with my first chronograph many years ago. One of those F1 red metal ones with the cardboard sun shades. Found how quickly those little plastic .30 cal sabots deviate from line of bore. They made pretty little star shaped holes in the card board at 5 yards from the muzzle. Lucky no damage to the important bits. I might have a go at 200 or 300 yards when my new Superchrono turns up as I should be able to put it well out of harms way.

Tussock, thank you. This is a battle I have fought for years and, after going through the whole explanation, I still get people asking what the (one) BC number for a bullet is. I do not ever mind the question and the explanation, it is the discarding of the explanation that gets to me.

Doesn't Sierra list multiple G1 BC's for their projectiles? I seem to remember Brian Litz saying the advantage of the G7 is that the BC has less variation as the velocity change

Originally Posted by Neckshot

Arnt G7 specific to boat tails??im just learning this shit.

Thats what I thought too

No G7's aren't specific to boattails, just that the standard G7 projectile is a boat tail, so a G7 BC is a better fit to boat tails than the G1 BC.
There are other ones as well
Copied from Wikipedia
The resulting drag curve models for several standard projectile shapes or types are referred to as:
G1 or Ingalls (flatbase with 2 caliber (blunt) nose ogive - by far the most popular)[11]
G2 (Aberdeen J projectile)
G5 (short 7.5° boat-tail, 6.19 calibers long tangent ogive)
G6 (flatbase, 6 calibers long secant ogive)
G7 (long 7.5° boat-tail, 10 calibers tangent ogive, preferred by some manufacturers for very-low-drag bullets[12])
G8 (flatbase, 10 calibers long secant ogive)
GL (blunt lead nose)

G1 BC projectile


G7 BC projectile