There is no 320366 mould listed in the Ideal or Lyman handbooks. You may have a “rare” misstamping, or maybe the second “3” got clogged or dinged and didn’t impress right, but that mould is the 323366, a Spitzer design for the 8mm Mauser. If it casts at 0.323”, the actual nominal diameter, you have a good one. Some vintage Lyman and Ideal moulds were cut with cherries that some forgotten gun writer described as being “made to the absolute maximum allowable oversize, then used and resharpened down to the absolute irreducible minimum.” It would be a rare cavity that was cut while the cherrie was “just right.”
I’ve sized and lubed 0.314” boolits, then sized them to 0.311” and finally to 0.308” without changing anything but the diameter. These were cast of Lino-wheelwright scrap. As others have mentioned, three thou is about it for a sizing step, and you will need the grooves lubed, both to keep them from smearing or collapsing, and to lubricate them through the smaller dies.
I’ve never done a boolit that “pointy.” Your top punch had best be a very good fit, methinks.