re: S&W model 10 which barrel length...4" 5" or 6"
My Model 15 with a four inch barrel just looks 'squared', just as when you see a Colt Peacemaker with the five inch barrel. It has that look of being complete.
Smith and Wesson M&P 'Victory' models, (M&P the predecessor of the Model 10) were 'squared' with a five inch barrel. Model 10's with a four or five inch pencil barrel are always 'square'.
Having since learned of a Model 14, as a target competition revolver, with it's six inch barrel, you would come to realize that anything shorter for a competition revolver, simply does NOT 'square'.
Lastly, my Model 15 'hangs out there', just as well, as my Browning High Power. Can't get any better than that, can you, or, CAN you?