In this video Rex will discuss bullet drag, ballistic coefficients, form factor, sectional density, the history of the G1 drag function, G1 VS G7 drag functions, and the effects of dynamic instabilities on bullet drag.
Definitions:
Ballistic Coefficient (B.C.) -- The ratio of The ratio of velocity retardation due to air drag for a particular bullet to that of its larger 'G' Model standard reference projectile due to air drag for a particular bullet to that of its larger 'G' Model standard reference projectile
c=WID^2
c = ballistic coefficient
W = mass of bullet in pounds
I = form factor (determined from a test projectile of the SAME SHAPE)
D = bullet diameter (inches)
Ballistic Coefficient = (Bullet Sectional Density) / (Bullet Form Factor- OF THE SAME SHAPE!!!)
Form Factor: A multiplier which relates the shape of a bullet to the shape of the standard projectile used to prepare the particular ballistic table.
Form Factor (coefficient of retardation) = (C.D. of any bullet) / (C.D. of the Defined 'G' Function Std. Bullet)
Coefficient of Drag (C.D.) = an aerodynamic factor that relates air drag to air density, cross-sectional area, velocity and mass.
Sectional Density: (weight multiplied by its frontal area) can then be used to relate the drag coefficient to different bullet sizes.
Dynamic instability has a tremendous effect on a projectile's trajectory. As the yaw increases, the drag increases, the bullet's velocity is far more retarded. These instabilities are not totally predictable and thus predicting and EXACT firing solution is very difficult.
LIST of Drag Functions and their applications:
G1 Standard model, Flat Based with 2 caliber (blunt) nose ogive
G5 For Moderate (low base) Boat Tails - 7° 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 with long 7.5 degree Tail Taper with 10 caliber tangent nose ogive
GS For round balls - based on measured 9/16" spherical projectiles
RA4 Good for .22 Long Rifle, which works out to be identical to G1 below 1400 fps
GL Old school model used for blunt nosed exposed lead bullets, identical to G1 below 1400 fps
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All the music in this video was created by TiborasaurusRex, an unsigned artist.
Song Title: Wadi Watir, Magnetic Night
Music and Lyrics by: TiborasaurusRex
Instrumentation and Vocals by: TiborasaurusRex
Recorded by: TiborasaurusRex
10 янв 2014
