I've been using Taylor's .60" Lee mould, but found it to cast .605" x .609" balls. So much for Lee moulds casting round balls. I've a number of them and none cast a perfectly round ball. Yes - I make certain they are closed properly.
Currently cast up several hundred .595's from my new Tanner mould and they run .595" - 598". Since I was using a .020" patch (mattress ticking) with the larger ones from Taylor's mould, I'll use the same patch witt the smaller balls from the Tanner mould as the fit seems good with a milder 'flat' brushed spot around the ball, punched in then pulled out with the strip of patching to check fit.
As to accuracy with the noted powder charge and patch/ball combination, my initial tests with this flinter off the bench showed 4" groups (with the odd fliers) at 50 yards off the bags using 3 drams (82r.2F). Most of the balls struck inside 3". It's an easy shooting combination that is very easy to load in my slightly choked barrel- 2 fingers on the rod down to the powder after short starting, yet the patches maintain their integrity.
I am hoping that further tests will tighten the groups somewhat. I'd like to hit the 3" consistant sized groups at 50 yards - no rear sight on this single short barreled fowler.