I have been fire-forming with full power hand loads seated out a lil further in this particular rifle,(custom chamber), but I can get close enough to the sweet spot to still get very acceptable accuracy. The rifle shoots great this way, and the brass is perfectly formed. Then I just moved on to 280ai load and it shoots even better.
It works good for me and I'm happy with this method. As far as factory ammo, I pretty much stay away.