You should always calibrate your Muzzle Velocity on the Kestrel because it accommodates for any errors. The suggested BCs are not always correct. We have seen a lot of muzzle velocity errors even with well chronographed MVs. Truing bends the algorithm to perfectly match the bullet’s flight path. Instead of hoping the prediction works, truing perfectly matches the flight path. For example, the ballistic solver expects different muzzle velocities depending on if you are using the G1 or G7 BC. However the chronograph is just measuring the actual muzzle velocity coming out of the barrel, independent of an BCs being used. Truing your Muzzle Velocity using CAL MV will always get you the proper MV to enter into the Kestrel so that your solutions are always on target.