JSB Exact King 24.39g BC

Have any of you calculated the actual ballistic coefficient for 25.39g JSB Exact Kings (.25 cal)? What have you come up with? I used the Chairgun calculator for muzzle vs. down range velocity. I am working up a new turret tape for longer ranges and am coming up with .0307 BC, with my Matador and .0302 BC, with my Synrod. I believe that .0360 is the indicated BC for a diabolo profile. Thanks in advance for your input, Steve.