I've owned a 6" in both guns and loved them. To be honest I don't know if I have ever even shot a 4" in either...maybe I should!
the 4 inch 617 is a little less bulky and a little more challenging for a plinking contest with your buddys / now the model 48 .22 mag does not have the bull barrel and much better balanced with the extra 2 inches . the 686 feels much better with the 4 inch than the 6 inch barrelI've owned a 6" in both guns and loved them. To be honest I don't know if I have ever even shot a 4" in either...maybe I should!!