Hello
My first post. I almost feel bad it is in here. I have a new (to me) model 27-2. The gun looks great and I had never noticed a problem until I shot it today (first time). Sometimes, not with any regularity the cylinder over-rotates. There may be a correct term for this. But the cylinder stop does not stop the cylinder where it should and the big heavy cylinder rotates the chamber in the cylinder past the barrel. A pull of the trigger will usually bring the next chamber in line. I have detail stripped and scrubbed the gun. But still have the same problem. Am I going out on a limb here in thinking I need a new cylinder stop and spring? I can't find anything else overtly wrong. It does this with live rounds, dummys and spent cartridges in the cylinder. That said I am no expert. Any comments or opnions?
Thanks Moose

Welcome to the forum.
Have you looked under the cylinder as you pull the trigger (don't do this with live ammo) to see if and when the stop is coming up? It may be sticking in the hole in the frame.

Update
After Bamabiker's post I went and looked at things again. The cylinder stop does not appear to be hanging up. You can rotate the cylinder slowly back into position and the stop rises up into the notch. Also when I had it stripped I could find no roughness or burrs in the area.
Thanks for the suggestion though Bamabiker.

The problem you describe is called throw by. It can be caused by a number of problems. If the stop is timed too late it does not have time to fully engage in the cylinder notch during normal rotation speeds. It can also be caused by the back of the cylinder notches being peened over from miss use. Also the lead angle on the stop may not be correct. A competent gunsmith can diagnose and fix this problem fairly easily.

I bet you need to replace the spring or it is dirty on the inside.