I tried working up 38 Spec. target loads for my 2" SP, and was getting 3-4 at best. The sites and sighting radius aren't conducive to great accuracy. If you access to a Ransom Rest, you can remove the human error. Having a good smith touch up the trigger will help too. I imagine 357 would have worse groups as the recoil is stout to say the least.
In my hands. . . not a very good group at all. In an olympic class shooter . . . much better. that gun was not made for 25 yard shooting. It is kind of like asking a how your kia will do on a grand prix course.
"The only senseless killing, would be the killing of me"