R Retardation fps.s.
V Velocity fps.

R=A*V^m

British 1909 Ballistic Constants

V(feet/sec)     A                       m

4000-2600       15366E-07               1.67
2600-2000       58495E-07               1.5
2000-1460       59814E-08               1.8
1460-1190       95408E-12               3
1190-1040       23385E-22               6.45
1040- 840       59939E-12               3
 840-   0       74422E-08               1.6