Now the hollow base wadcutter. Target shooters wanted a little recoil as possible consistent with winning scores. We all do out best with less recoil, so how do they get the best accuracy out of powder puff loads in the 38 Special. The answer was the hollow base wadcutter.
The hollow base shove the center of gravity forward and things tend to fly true that way. Think of a shuttle cock and you will get the idea. The notion was not to allow the skirt to expand and fill the cylinder throats as some folks posit.
The HBWC is a real special needs child. This is where the wadcutter brass is almost necessary, as the long parallel sides of the base gives room for the longer HBWC to fit without hitting the taper toward the bottom of the case and crushing the fragile skirt. An extra long expander really helps in this regard.
I see no purpose for HBWCs, off the paper target range, but for that purpose they really shine. Depending on design, push one too fast and you run the danger of blowing off the skirt, leaving a barrel obstruction behind for the next bullet to encounter.