The "V0" velocity is not actually measured, it is calculated. The Labradar doesn't start tracking the bullet until is is approximately 10-15 yards downrange, and it measures the constantly from that point until it no longer sees the bullet (distance) or the bullet hits the berm. It extrapolates the V0 (muzzle velocity) based on all the measurements to determine how the bullet loses velocity over distance.
The Labradar creates a file that shows the actual velocities measured as the bullet is going downrange. It puts it in a subdirectory labeled "TRK". It would be interesting to see that data.