1. The molecular velocity stat' most likely to be relevant is, not the average velocity, but the RMS velocity, since this is the one that corresponds to average kinetic energy.
2. An air temperature of 40C = 104F produces an RMS velocity of 519m/s = 1703fps, and air reservoirs are often this warm (or even far warmer) after a recent fill.
3. There are many ways to inadvertently perturb the calibration of the readings from a Shootin' Chrony chronograph by 6% (or more), and 1750/1650 = 1.06.