Rice barrels in .50, shoot very nicely with a .495" ball (normal .005" under) and a .020" to .022" patch.
Just to show what a good crown allows, we loaded a .508" ball in Taylor's Virginia rifle, Rice barrel, with a .019" denim patch, then pulled the ball with the patch strips 'wing's' and the integrity of the patch material was unharmed by the lands.
The balls must be pure lead. WW is not pure lead.
While that works with a good crown and .016" deep or shallower rifling, doesn't work well with .030" rifling. Usually one must try this themselves to understand what's happening.