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Functions for Calculating the Retardation of Standard Projectiles
Retardation is calculated according to the formula R = Av^{m} , where R is the retardation of the Standard projectile under standard conditions, v is the velocity of the projectile and values of A and m are shown in the tables below. To find the Ballistic Coefficient, C, it is necessary to use the value of R in the formula C = R/r, where r is the measured retardation of the projectile under test. In practice, 2 values for R are derived from the measured Initial and Final velocities of the test projectile, the mean being used to find C. Values for A and m change with velocity, since the drag forces, acting upon the projectile, vary with its velocity. These velocity ranges, as well as the functions associated with them, differ slightly according to the data from which they were derived. The, British conducted, firing tests, between 1904 and 1906, provide the basis for the retardation functions in the first table. The second table shows those used to formulate the American Ingalls’ Tables, derived from Krupp’s firings of 1881 and the work of Mayevski.
British Functions of Retardation for their 19041909 Standard Projectile 

Velocity Range (fps) 
Value of A 
m 

From 
To 

1 
839 
7.4422 x 10^{  4} 
1.6 
840 
1039 
5.9939 x 10^{  8} 
3 
1040 
1189 
2.3385 x 10^{  18} 
6.45 
1190 
1459 
9.5408 x 10^{  8} 
3 
1460 
1999 
5.9814 x 10^{  4} 
1.8 
2000 
2599 
5.8494 x 10^{  3} 
1.5 
2600 
4000 
1.5366 x 10^{  3} 
1.67 
Mayevski / Ingalls Retardation Functions for Krupp's 1881 Standard Projectile 

Velocity Range (fps) 
Value of A 
Value of m 

From 
To 

1 
789 
4.6762 x 10^{  5} 
2 
790 
969 
5.9353 x 10^{  8} 
3 
970 
1229 
6.3368 x 10 ^{ 14} 
5 
1230 
1369 
9.5698 x 10^{  8} 
3 
1370 
1799 
1.3160 x 10^{  4} 
2 
1800 
2599 
1.2480 x 10^{  3} 
1.7 
2600 
3600 
4.0649 x 10^{  3} 
1.55 