Mag Cannon from JTAS Vol. 8 Question


I'm having trouble understanding the Mag Cannon from JTAS Vol.8, and what kind of ammunition it uses. It's stated that it can use "most ammunition types available for heavier weapons." I assume that's referring to the specialized ammunition in the CSC, but I don't understand how that interacts with the two different firing modes of the Mag Cannon. The direct fire mode lists a normal damage and cost for a magazine, while the indirect fire mode and belt/smart box entries reference using grenades as ammo. Is this essentially just a gun that can swap between firing grenades and normal slug ammunition, or do both firing mode shoot grenades but the direct fire mode has different damage statistics for some reason?