I know that the Big Boar is a 1-48 twist but according to the people I talk to that own them, they shoot roundball real well. .58 caliber conical bullets are hard to find and expensive. Also nothing walks off from a .58 roundball. One person I know that owns that rifle shoots 110 grains of 2f and a .570 ball and patch.
I have a .58 caliber also but mine has a 1-70 twist. Mine shoots 110 grains of 2f and a patched ball as well. Start your testing out at 80 grains and work it up from there. That is a great rifle. I still kick myself when I had a chance to get one and passed on it.
I have a Navy Arms .58 Hawken hunter @6 " barrel ,1 in 60" twist . It will burn Up to 175 gr of ffg ,with a wad under a patched RB. It stays on a 8.5x11 paper off hand at 50 yards .This load came from the late Val Forgett, and may exceed your comfort level
A moose hunter I guided had one of them. He'd put a ball in his hand, and pour on enough black powder (goex ffg) to cover the ball. That did the trick, as Cayagud confirms, a 56 inch bull did not "walk off". He tried to, but went down after a very brief stagger. The bigger diameter ball you have should work just fine in 1 in 48. If I didn't need a scope, that caliber (at least) and round ball would be my choice. Just plain fun to shoot those RBs. Beats heck out of the cons.
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