I've won several matches with my flintlock where 3 shots were in the10 ring...Out to 100 the limiting factor now a days is my eyesight...In Ned Robert's book, he mounted a scope on several Hawken style rifles and did some impressive shooting...If I have time I'll dig it up and see exactly how good...

At any rate, 100 yards is no problem with patched balls, as long as it ain't windy...
With open sights, 100-125 is about as far as most need to be shooting anyway...