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ARMAG

Search matches names, aliases and the text of every page. An arm found by its service designation is found by its alias, not its title.

Ballistic coefficient

A number describing how well a projectile keeps its velocity against air drag, relative to a standard reference shape.

Also called BC, G1, G7

Not a property of the bullet alone. A ballistic coefficient is the ratio of the bullet’s sectional density to a form factor measured against a specific standard projectile, so the same bullet has different coefficients under different standards.

Two standards matter here. G1 is a flat-based reference shape from the 1880s and is what most American ammunition makers publish; it fits blunt flat-based bullets reasonably and long boat-tailed ones badly, which is why a G1 coefficient often has to be published as several values for different velocity bands. G7 is a boat-tailed reference shape and describes a modern long-range rifle bullet far better across its whole flight.

This site stores whichever the source published, labelled, and the trajectory solver uses the matching drag table. Mixing them silently would produce a plausible and wrong answer.