Interesting, Bill. I have seen others, (was likely DPhar) note that in charges too large for the calibre and ball/bullet, that Swiss fouled.
In my .69, I found fouling not to be a problem as high as 200gr. GOEX 2F. That was not fun to shoot, but no fouling problems, shot to shot.
I have not tested Swiss 1 1/2F in it, yet. Probably won't.