Even with up to 200gr. in my .69 - zero fouling buildup between shots. I've never had fouling buildup between shots since about 1973. That's when I read Ned Robert's book(& Corbin's book) and
re-crowned the muzzles to a nice smooth radiused crown which allowed nice snug loads without patch damage. These gave improved accuracy.
In my .58's with slow twists, 72" in the Zouave and Numrich and 66" in the Large, I used 120gr. in the first two and 140gr. in the Large barrel to get the best accuracy. In those days, I was only shooting at 100yards. Those loads produced the smallest groups in all three rifles. Less powder opened up the groups. For example, in the Large barrel, 90gr. 2F would not stay on a pie plate at
100yards. Useless, imho.