My first Ackley improved cartridge was the.243AI, Sierra's tech line advised that I utilize a cheap bullet loaded long enough to jam into the lands when the bolt is closed (same function as Roy's ghost shoulder) with a load toward the max end of the spectrum for that bullet.
that particular method had formed hundreds of .243AI & 6mmAI rounds for me to great effect.
In a particluar 6.5-06AI that I load for, we use the cornmeal method described above (with a little less powder
). The shoulders aren't perfect but close, the next firing established sharpness of the shoulders.