Well, it is not 'normal' to load, and not reload. You'll need to stick to your choice here, so consider it carefully.
I guess that explains the extreme spreads in velocity, -until against the lands.
New brass dampens the pressure peak, as energy is used to expand that brass.
Fire formed/reloaded brass fits tighter to chamber, so it expands less to reach chamber dimensions. Less energy wasted means higher energy pushing bullets, means higher muzzle velocities. It also provides more consistent pressure peaks, so lower extreme spreads in velocity.
Having bullets against the lands causes a higher starting pressure (pressure needed to move a bullet).
This hig her starting pressure allows more time for your cases to expand before bullet movement, effectively fire forming cases -during the shot. It's normalizing case dimensions, and look how low velocity ES was with that.
But if best seating is not against the lands, as your testing shows, you could carefully find another way to raise starting pressure.
This can be done through higher neck tension, or a bit faster powder.
You can also seek a bullet that likes to be in the lands (ITL).
You could keep tweaking around 75thou OTL, and around 82.3gr, for ~.6" grouping.
But that's not going to help you at further distance with that ES. Accuracy will be especially dubious.
If it were me, I would seek good factory ammo (for your gun) and forget reloading (if I just didn't want to reload).
If you change your mind about reloading, keep in mind that velocity could go up, or down(depending on load density). So back off to like 81.5gr and work up the first time. And then just start over with powder development.
Brass typically takes 3 firings to fully fire form and reach stability. With that, you should not need high starting pressure, particular bullets/powder, or any other special actions.
