BfX is based on the book of Arthur Pejsa. Pejsa deploys the Siacci method for approximating bullet trajectories. For a broader discussion on ballistics, see external references and Wikipedia's pages on exterior ballistics in English or Dutch.

The algorithms implemented within BfX are derived following Pejsa's approach. As a consequence, original typos have been bypassed, formulas incorporate direct metric constants, unnecessary approximations are skipped, the range of applicability successfully extends below the speed of sound, and BfX natively supports multiple drag functions. The underlying mathematical derivations were processed and verified using Mathematica, a computer algebra system designed for rigorous equation manipulation.