Re: 2 roundball load????
You build up recoil, have one ball possibly acting as a bore obstruction, have accuracy issues with the second ball as it comes out onl;y to be hit by the patch from the lead ball, etc. I have never done it. see no reason to.
In the revolutionary war days, a frequent load in smoothie muskets was a buck and ball. A ball down first on top the powder and some buckshot on top of that. Standing in a line facing off at the enemy line at 75 yards, I dare say I'd want even more than that. (perhaps an uzi?)
I shoot for accuracy with my rifle and patched round ball, I can't see why I would intentionally throw my accuracy off. if I want multiple shot spraying an area, I'll take a smooth bore and shot.