I'll put in my two cents.
I've had two SP101's.....a 3" 38 spl. one. made in 1989 (the first year of production).....and a 2.25" 357 mag, made in 1994. Both were very solid, well made and functioned 100 %. I love the modular design and the solid frame. I also really liked the looks of them.
However, both of my SP101's were disappointments. First, I found that the sizing of the chamber throats was all wrong. Apparently this is common with Ruger revolvers. This was true of BOTH guns. The chamber throats were very tight, smaller than the barrel groove diameter. (Chamber throats should always be 0.005 - 0.002 LARGER than groove diameter.) Accuracy problems, leading, etc., were the results of this. So, I recut the chamber throats.
Next, the forcing cones on both SP101's were poorly done. Ruger uses a 5 degree angle for the forcing cones, which is only good for jacketed bullets. Cast bullets virtually require a 10 degree or greater cone angle. Further, the cone on the 2" 357 gun was absurdly deep (over 1/2") and couldn't be recut without leaving a step, which is terrible for accuracy/ leading. The cone on the 3" gun was considerably better....and I was able to fix this one.
Lastly, both guns had slightly over-torqued barrels. By coincidence (or not), both SP101's shot consistently 4" or so to the left at 10 yards, even off a rest (and yes, multiple shooters, different ammo, etc. etc. were tried). Never was able to completely solve this one. It obviously would have required realigning the barrels - but by this time, I was a bit discouraged with the Rugers.
So, in the end, after all of the effort....the SP101's went away. Even after the effort I made with them, they still never shot as well as my S&W K-frames, which required no tweaking. A BIG disappointment for me, because I wanted an SP101 for a long time before I got one......and I REALLY wanted them to work for me. I never seriously considered contacting Ruger about these, as the guns were older production. Perhaps I should have tried that route.
Anyway, I post this story simply by way of telling my true experience with the SP101's. I will NOT bash Ruger, nor would I ever presume that all SP101's would have the same issues. In fact, I would like to have another SP101, IF I could be sure in advance that I wouldn't have to deal with these problems. I consider the SP101 to be a great design and a great revolver, unfortunately (in the case of the two I tried)....let down by poor execution.
As I said, very disappointing. But, I've moved on.