G4 drag coefficients

[Whaump 'em]

Does anyone have a link to, or have you seen, or even heard of these tests on the .50 BMG bullet that are the basis for ballistic coefficients?

[wiljen]

The tests that led to the development of the "G" Drag functions were conducted by the US Army Ballistics Research Lab (BRL) at Aberdeen. The functions were actually published not by the army, but by Winchester-Western in:

"Exterior Ballistics of Small Arms Projectiles" by E. D. Lowry, May 4, 1965. Research Department, Winchester-Western Division, Olin Mathieson Chemical Corporation.

WW published bullet drag ("G") functions for many standard projectiles of different shapes including one to replace the original Krupp projectile as used by Ingalls designated "G1". The refined G1 standard projectile was still flat based with a 2 caliber ogive but it's length was extended to 3.28 calibers with a body nearly 2 calibers long to more closely match the proportions of modern artillery rounds.

Although, the BRL had demonstrated modern bullets would not parallel the flight of the "G1" standard projectile, the "G1" drag model was adopted by the shooting industry due to its simplicity and is still used to generate most trajectory data and B.C.'s. These are at best approximations as differences in bullet shape and velocity will cause differences in BC.

Current models applicable to small arms are:

G1 - Standard model, Flat Based with 2 caliber (blunt) nose ogive

G2 - Special model for a long, conical point banded artillery projectile
with a 6 deg boat tail. Not generally applicable to small arms.

G5 - For Moderate (low base) Boat Tails - 7 deg 30' Tail Taper
with 6.19 caliber tangent nose ogive

G6 - For flat based "Spire Point" type bullets - 6.09 caliber
secant nose ogive

G7 - For "VLD" type Boat Tails - long 7 deg 30' Tail Taper
with 10 caliber tangent nose ogive

G8 - Flat base artillery projectile with similar nose design to G7.
Also applicable to small arms projectiles

RA4 - For 22 Long Rifle, identical to G1 below 1400 fps

GL - Traditional model used for blunt nosed exposed lead and hollow point
bullets, identical to G1 below 1400 fps

I'm afraid I can't help with the G4 functions as I have no reference on that function. I have the tables for G1,2,5,6,7, and 8 if you have an interest, PM me with an email address and I'll send em your way.

[Whaump 'em]

Thanks wiljen.