I have Red Dots on my 686 with 6" barrel, my two 625's, my 16-4 (6"), my Custom 1911, my 520 (4"), and my 629 Light Hunter, etc.,etc.,
After losing the vision in my right eye (I shoot right handed), I tried a Red Dot and ended up putting them on nearly everything I shoot. The Red Dot sights enable me to "get my mojo back"...
I bought my 6" Model 686 from an estate sale. After I got it home and started shooting it, I noticed it spit a bit and the barrel cylinder gap was wider than my preference. I had my pistol smith, Jack Basham of Cincinnati, Ohio, set the barrel back and give me tight clearance in the barrel cylinder gap and re-throat the barrel. My first trip to the range, shooting standing at 25 yards (with the Red Dot Sight):
So, go for it!
Dale53