I have a 4" M10-5 which I got cheap years ago from a local guy who is into high-end collectible S&Ws (he has five pre-27 3-1/2" Magnums) who sometimes had to take the chaff with the wheat in his deals, so to speak. I was glad to take the chaff. I sent the cylinder and thumbpiece to Clark's, where they chamfered the chamber mouths and relieved the thumbpiece for speedloaders. Then I had a local guy re-blue it, which it badly needed. This was all pre-2005 because the guy who re-blued it left after Hurricane Rita. I carried it and shot it occasionally, using the R-P version of the FBI load for carry and my 158-grain handloads for practice. After all, it's a fixed-sight K frame, what else would you shoot in it? I was heavily into IDPA at the time and practiced exclusively on IDPA targets with that big 8" -0 zone. After that, either my daughter had it or it sat in the safe.
I got it out again recently and for the first time since I've had it benched it and shot it on a B-8. It was about three inches high and two to the right at ten yards using my 158-grain handloads. Oops. I have some 125-grain handloads I use for my 642 because that's what it's regulated for, and took them today with the 10-5 and tried again. They went maybe an inch below the black (using a six o'clock hold) and a bit to the right. I know that my groups benched are a little lower than when shooting off-hand, so I tried a couple of goes at the Five Yard Roundup using the 125s and ended up with a 94 and a 97. I'm going to go back out there with my remaining Ranger Bonded and HydraShok Deep (and a flat file just in case) and verify POI both at ten and 25 yards.
I've got several 4" K frames and the 10-5 is the lightest among them. My freestyle splits on the drills were in the .3x ballpark with almost all of them in the 10 ring, so recoil isn't a problem. It moves handily, like my 3" M10-7. I don't know if this is going to become my main carry revolver, but it's in contention.