so I brought home an older police radar today and we measured some tee exit speed
Be aware that some radar guns show average speed, some show last speed.
I would not rely on any radar gun unless it shows two speeds on each reading - fastest speed and last speed. Ex. ball out of the hand, and ball as it reaches the plate. Then, only rely on the speed if there is approx. 9-11 mph difference for fastballs.
Many times, I will take a reading and there is only 4 mph difference, or no difference. That means I pointed the gun near the plate, or halfway, or the batteries on the gun are getting weak, or I'm too far away.