Doug, I have seen this on several different Dan Wessons, including on e that I have now. The probable cause is that the crosspin hole in the rear sight body is oversized - and it allows the rear sight to "wobble" on the pin. I have seen this several times. Only definite fix would be to drill the frame of the gun for a larger pin - but, who would want to do that ! You may try a bit of shim stock underneath the front of the sight - (in front of the elevation screw). This would apply a bit of upward pressure and may tighten things up a bit. Or, if you are always going to shoot the same load and sight settings, you may shim the entire rear sight assy. to tighten it up. But then you would lose the adjustability. Good Luck !
