Would be willing to bet he's using a Shooting Chrony. Have seen one of them jump 10% in velocity due to a change in the light.
The magic new velocities (which amount to maybe 100 fps) in the .243 with Enduron powders are most likely due to using more accurate piezo-electronic pressure-test equipment, rather than older copper-crusher equipment. If you look at Hodgdon's data on their website, it shows the pressure for the Enduron powder in PSI (electronic) rather than CUP (copper crusher. Hodgdon has not made any claims about higher velocity levels with the Endurons.
