I have a 627 when cocked the cylinder has no play. On my 624, there is noticeable movement when cocked and rocking the cylinder. Seems to me this would affect accuracy as the bullet enters the forcing cone a tiny bit different. I don't have the tools to see how much it's moving, but it seems any is too much on a revolver with probably 500 rounds through it. Can anyone help?
Your 627 must be an acception. All of my Smiths have a slight bit of rotational play when cocked. The cylinder stop is never an exact match for the notch on the cylinder.
A little play is actually an advantage when the gun gets dirty, or to allow tiny alignment corrections by the bullet when shot.
You can't tell the accuracy of the revolver by wiggling the cylinder; some of the tightest ones are not the most accurate.