Partial FL means using a Full Length sizing die in a manner that only partially resizes the case. This is comparable, and in some cases superior to neck sizing. Its achieved by leaving a gap between the die and the shell holder (I use a toonie).
The easiest way to do this is to loosen the lock nut and turn the die back half a turn and reset the lock nut. After the first sizing there might be a double shoulder where the shoulder and neck meet. Ignore it and continue on.
This is actually a common thing to do with most rimmed cases.


















































