The reg seat will definitely cause inconsistency. The consistency of the paint is the biggest factor in velocity consistency if the valve is working properly. Other items are really just factors in rates of fire or efficiency.
Originally Posted by Mr. Red
The ratio of change isn't going to be a big factor. The tank regulator output does lower as the tank empties from 4500 psi to 800 psi. The change depends on the regulator used on the tank. Being that the output might change by 50 psi (extreme case) from full to empty, the AIR valve might change by 5 psi (worst case at 10:1). Since the operating pressure in the chamber is over 350 psi in a level 7, a 5 psi change would only be a 1.5% change in pressure which would impart less than a 1.5% change in velocity at the upper end of the operating velocity range. At 1.5% change thats only 4 fps. So, looking at those numbers, any change in velocity would be less than 4fps for any spike in pressure around 50psi. The numbers I used are not truly accurate AGD numbers. I really don't know the AIR valve ratio, but I suspect it is actually much greater than the ratio I used for explanation purposes, so the numbers should be better than my worst case scenario.
Except for the Automag in front, its usually the man behind the equipment that counts.