About all ML barrels made today have good round ball twists. I have proven to my self, that a nice snug load in a .58 will shoot well from 48" twists
to 78" twists. The 48" twist & 72" and 78" twist bl'd rifles were all military rifles. The 66" twist was an inch and an eighth octagonal Hawken bl.
The 78" twist military bl. shot really well with 85gr. 2F, as did the two 48" twist mil. barrels. The 66" twist did not like less than 140gr. 2F, while the
72" twist military rifle preferred 120gr. 2F. This simply shows guns and barrels have their own rules. There are general trends as Hungry-Horse and Bob
note. Usually the slower the twists, the more powder is required - but not always. In my tests, the slowest twist I tested, shot best with the same powder
charge as the fastest twist. It shot as well, with a LOT more powder, but that charging was not necessary.
How much powder you have to use depends on what you want from the rifle. In the days of testing those bls. I was interested in shooting 50yards for
sight adjustments, and 100yards for groups.
They all shot well at closer ranges - of course.