use a good case expander ,not just a flaring die . Weither hollow or solid the bases go deep into the cases & is subject to being "sized" down especially on the swaged or soft cast varieties.
Hollowed based your kinda limited to how low or hi to go with the charge , not enuff & the skirt does`nt flair to seal the chamber , to hi & ya blow skirts .
Solids offer more flexability but must be fit to the firearm just as anyother cast boolit to see best results .
Some WCs have a crimping groove , you can use that or seat flush with a slight roll crimp to ensure the case will fit , no taper or profile crimp as your dealing with soft lead likely!