I was reading P.O. Ackley's loading manual the other day it it struck me that he strongly supports using full loads to fireform his cases. In fact, he states that if a light load is used it can shorten the case and change the headspace of that cartridge. This is potentially disasterous. He states cases and shows pictures of rifles blown up by this practice.
This only applies to rimless cases that headspace on the shoulder. With rimmed and belted cases it doesn't matter if the shoulder is set back.
This is old, and needs to be renewed as a warning.