Still no personal experience with Swiss powders in a muzzleloader, but I have to comment on Herb's extreme spreads. They seem VERY extreme to me.
I haven't "done" extreme spread spread tests for a while, but in all calibres I did it, using GOEX powder, even back to the late 1970's and up to the 2010,
my spreads in all calibres from .32 to .69 were single digits. Perhaps this is due to a lack of blow-by, or due to using tight enough combinations that make
the powder burn better/more completely?
I did notice Herb mentions using a .013" patch. My patches measure from .021/.0235" in the smaller calibres to .034" in the .69. This is with balls that are .008"
under bore size, on up to bore size in the .32, .36 and .69 and in the .40, .002" larger than bore size. I used a 10 ounce denim in the .69, with the .690" balls.