Both bores measure .366. The round action has a twist of 1/25 and the other rifle is a 1/50 twist. Both of my molds cast heeled bullets. One is 135gr and the other cast 86gr. Its almost a round ball with a tail. I have tried Unique, Bullseye, 2F 3F and Tripple Seven. It's strange but I was just looking at those bullets today thinking I should try again.