B. C. or Ballistics Coefficient

B. C. or Ballistics Coefficient and Retardation Tables

The ballistic coefficient is a number that relates the air-drag deceleration of an actual bullet to the air-drag deceleration of a standard bullet. Extensive testing was performed to determine and record these air-drag or retardation values throughout a useful velocity range. These retardation values are then listed in a table ( usually in 10 feet per second intervals ).

The most commonly used table is referred to as the G1 table and was tabulated using the retardation values of a projectile weighing l pound, with a diameter of 1 inch and a nose curvature having a radius of 2 calibers ( or two inches ).

A smaller diameter bullet of lesser weight will posses lesser inertia than that of the standard bullet and will not pierce the air as easily as the standard bullet. The result of this condition is that the smaller bullet will posses larger retardation values spanning the useful velocity range than the standard bullet.

If the actual bullet produces retardation values that are double those which the standard bullet produces, then the actual bullet may be compared to the standard bullet with a coefficient number obtained by dividing the retardation rate of the standard bullet by the retardation rate of the actual bullet.

The result of this division is a G1 ballistic coefficient of 0.500 for the actual bullet. [Standard Bullet Retardation] / [Actual Bullet Retardation] = Ballistic Coefficient of the Standard bullet.

This ballistic coefficient is valid only for the G1 Retardation Table and would have no useful application with any other retardation table.

This software offers the use of tables modeled after 5 different bullet configurations :

G1 - Usually the industry standard for jacketed, flat based, pointed or hollow-pointed bullets and also for most cast lead rifle and handgun bullets.

GL - For spire pointed, lead tipped projectiles where the soft lead nose deforms at higher velocities. This table is identical to the G1 table at velocities below 1,300 f.p.s..

G5 - This table conforms to the boat tail, spire pointed, jacketed bullets.

G6 - Full metal jacketed, spire pointed, flat based bullets conform well to this one.

RB - The British Round Ball Test firings were used for this one.