As a funny aside, I forget to mention that last summer I went to a range with about a half dozen friends. I brought my 4" Ruger Service Six because I was fixing to head to Colorado and bear country and I didn't want to put a fancy S&W in my luggage. The gun was to accompany me solely at my friend's house as we hung out on the veranda in case of incoming critters.
Anyway, I fired a lot of rounds through it to refamiliarize myself with the gun because it had been awhile since I used it. Meanwhile, my friends were shooting a variety of modern semi-auto pistols. At one point I turned to one of them, who seemingly couldn't get a solitary good group with his pistol (a Glock, I think) and I said, "Do you want to shoot a real gun?" One round fired, one bullseye later, he sheepishly admitted he totally sucked with his pistol. I didn't blurt out "NO KIDDING??!!" but I mildly agreed with him and recommended a switch to revolvers.
That 4" Ruger Service Six is a heavy duty, non-recoiling beast - if the GP-100 is as good, with or without adjustable sights, "it'll do!".
I can't attach a picture. I left the gun in Colorado so I don't need to drag it along next time. Oh, well........