Rio, Great find and it sounds like a very reasonable price too....I'd have walked out with that one myself.
Just thinkin out loud...that one cylinder that's throwing the shot high might improve with a cylinder throating job...or might not too...those are really nice groups and personally, I'd be inclined to leave it alone....marking that one and going with the other five. I've got an equal number of old model Rugers and new model ones as well as a Colt SAA that I shoot often enough to settle on the old: 'load one, skip one then load the rest' method of loading five...it works for me and keeps my loading blocks evened up shooting only five at a time.
With a 7-1/2" bbl'd Colt SAA, shooting from Keith's old long range position (sitting, back rested with gun extended between knees), I see a 2" difference in impact points between my 255 gr RN, flat points (Lyman's 454190 mold) and 200 gr LSWC's (H&G's #68) with the same powder charge (8.0 gr of Unique). Both will group into ~2" at 25 yds that way, and I find, at least in my hands, the Keith position duplicates an offhand, two-handed Weaver Stance impact point...it's also every bit as accurate as shooting off bags. I'll add one note on Keith's position...it's hell on the inside of your Levis...the cylinder gap flash quickly gunks them up and it's definitely NOT a position for shooting in shorts!
In my hands, again, bag shooting results in a lower impact point as well as requiring a different windage adjustment...it might be different for you, but you're an old time LEO and know the in's and out's of your personal grip changes and recoil anomalies; bags vs. offhand.
BTW, my Smith M-25 gives me the same impact point difference...
Lastly...hell...those great groups are just a smidgeon off....looks like an inch from the pics...and the rear sight is bottomed out...you may have more than enough up & down in it to correct. I'd hate to take a file to that front sight my self.
Best regards, Rod