The chamber mouths are round, the sides of your calipher blades are flat. You get something like this: (I Try using only the tips and realize you're still going to be approximate, not right on the money. Accurately measuring holes is done with pin gauges for a reason.

Looking at the length of those bullets but being unable to measure them, I'd be reluctant to try to seat them flush with the case mouth as you're reducing effective case volume. Match them up with some truncated cone shape 230 gr and see where the base of the bullet would be if seated flush. Load tables are based on the assumption that the base of the bullet is going to establish a given case volume. Flush seating of a wadcutter designed for a much longer case is going to make major changes in case volume.