@admin
Which book did you used for BfX ?
Modern Practical Ballistics by Arthur J. Pejsa ?
Ja,
however the book is full of typo's, you have to follow his derivations, and redo the math. Alternatively you might to use the book of Robert McCoy Modern Exterior Ballistics 2 (no 1 has many typo's too).
In BfX I have generalized Pesja's approach a bit.
Robert.