One of my favorite rifles is a Mauser 98 based 30-06AI which I built back in the 70s. Fireforming brass is easy, using a clean and un-lubed chamber and factory 30-06 ammo. I usually neck size only and check brass for proper chambering prior to loading. You can load the improved rounds to approximate the .300 Win Mag ballistics. You can also shoot standard 30-06 when you want and come out with your improved brass as a result.
Dosn't matter what day of the week it is, the best day is the day with your finger on the trigger--jra