I don't think Dakota's results are bad at all;there's slight loss of velocity but not enough to worry about.
I can't help but wonder if Sam's lower POI is the result of lower velocity due to low temps, or simply shooting through cold,dense air.Match shooters I know back here have to make corrections in colder temps for long range;wonder if it's lower velocity of ammo or air density(?)
Some match shooters have told me they use Hodgdon Extreme powders,finding them more stable in temperature extremes from winter to summer.They push their 223's pretty hard for LR and blown primers in the summer pretty common
