The full length sizing die included with the PaceSetter die set is not technically a case forming die. There is a certain amount of spring back in the brass case, and this spring back has to be taken into consideration when designing the die and its intended purpose.
Case forming dies usually need to be made to smaller internal dimensions to compensate for more spring back, because the case dimensions are being altered to a greater degree. Sometimes a full length sizing die will work as a case forming die, but it depends on a large number of variables, and is impossible to predict with any accuracy.
