I just listened to episode 60 of the Hornady podcast "it's time to answer some questions."
Part of the discussion was about how in their testing, with increased powder charge, they typically saw increased dispersion. I think they said it didn't always get worse as powder charge increased but it never got better.
I'm of the understanding this is because you're increasing the rotational RPM of the bullet, which would exacerbate any out of balance condition whether that's caused by a manufacturing defect or by some reloading process that isn't 100% perfect.
I see some guys shooting some very small groups with pretty high velocities and I'm hesitant to drop charge weight because I don't want ES/SD to increase.
Are any of you guys getting real small groups at or near ACTUAL max powder charge (not book max) or are you dropping it down a hair and accepting a slightly higher SD/ES?