Conical. Accurate molds is who is going to make the mold. I have a TC 370gr maxi ball and the Lee 250gr and 320gr molds. These shoot ok at best. I don't want a tapered bullet like these are. I feel that is why they don't shoot well at all.
I have tried several types of black. Swiss, Diamondback, Wano, Goex. Plus some of the fake powder. I have tried a 50 cal and a 54cal felt wad lubed and unlubed. Have used TC bore butter. Made my own with beeswax, olive oil and lanolin. Beeswax and crisco. None of the lubes have made a difference one bit. Groups never got larger or smaller. But the wads made the biggest difference. Cut the groups in half. But 4" at 100yds is too big. It shoots a unmentionable bullet at a 1.25" at the same distance. Tapered bullets just are not accurate in any type of firearm. Gas getting past the base is a disaster and leads to poor accuracy and unstable bullets. And I think that is why the wads made such a big difference.
I have been a very successful pistol and rifle bullet designer. I know what it takes to make them shoot. But black powder bullets are new to me and I want to figure out what it takes to make them shoot. but custom molds are expensive. I don't want to have to get several molds made to fit this gun. I want the first mold to have the best design so I will not have to get another one made for it at a different size.
I guess I can just order it oversized and size it to what I need. But that introduces its own set of problems. Sizing dies are easy. I have a lathe and can make whatever size I need. But I would rather not have to go that route. I was hoping someone could say "this is what most ML need as to size." Regular cast bullets need 0.001"-0.002" oversize at the most.
I don't know what ML need. Hence asking here. I am guessing at least 0.001"-0.002" under bore and groove? That way they can still be pushed down the barrel?