[Oblofusc]

. . . uses the same core pin (the part that makes the hollow base" is the same as the ones used for the "regular" minie ball mold"

Reason I ask is because I know from experience that a core pin for the Lyman .58 cal "611" thick skirt mold is a larger diameter and will NOT work with their regular .58 minie mold.

[Hellgate]

I have both the 575213-OS and the 577611 and they look like each has the same thick skirt compared to the other minie molds from LEE.

[RaiderANV]

It's a good chance it will be a slightly if not more different dia. where it enters the mold and will allow lead to give the bullet a halo around the bottom if you will