load your .223 with BL(C)-2, H-335, Varget, AA2230, Win 748, or even IMR 3031. I like ball powders because it runs thru equipment so well.

It's not at all likely that Winchester will let anyone know what they load their factory ammo with. Be very suspicious of folks that say they know ....they may or may not.

Any of the above powders (or others as well) are very capable of giving you the accuracy you're used to.