I posted earlier that I had picked up a pair of Greener Martini actions at a local gun show. I have made my mind up to build the first one into a 12 bore rifle, primarily for round balls but with the possibility of shooting some conicals. I believe I'll go with a straight octagon barrel.

I'm planning on using the Magtech brass shells and from what I understand they run more towards 11 gauge as far as internal dimensions for wads. Would that make it so a guy would need a .751 diameter ball, with the barrel having a groove diameter of around .741 or could I get away with a standard .729 12 bore diameter ball and the appropriate bore dimensions.

Thanks in advance guys.

Mart