I just got back to this jewel after plowing and shoveling snow for two days! The bores are of a slightly different size as it says in the description. I used my digital caliper to come up with the groove depth. The ball, or bullet size is going to be an 11 bore.

R 18.9 mm--.744--gr .754
L 18.8 mm--.740--gr .750

A .754 groove dia pure lead ball weighs 643 gr. (calculated). Accurate molds make several different style of bullet molds starting with the 74-700 at about 700 grains that you can tweak (enlarge) up to .015. There are other changes you can make too. So do I go with a round ball, or a bullet, and what size? Thanks, ED

https://accuratemolds.com/catalog.php?page=33#catalog-anchor