I'll second the Weigand rail, below is my 620 with a Nikon Monarch 2 x 20 EER on a cut down full length rail originally purchased for my 6 inch 617.



Note that while it appears that the scope might interfere with cocking the hammer it was NOT a problem. I'll also note that the magnification for this scope is only 1.75X actual and for my eyesight I'd consider it suitable for 50 yards or less, it's not an optimum choice for shooting at 100 yards or more. Fact is at 50 yards a 12 inch target looks pretty darned small.

As for why I put a scope on a 4 inch revolver, I did it to simply satisfy my curiousity, which I did. Before the scope shot loose I managed to put 4 rounds into a 7/8 inch group at 50 yards. BTW, consider that another tip, the mounting clamps will shoot loose so to avoid learning this the hard way, check the clamp screws for tightness at every break in the action.

BTW, one additional tip, do NOT try to use Burris mounting rings, they do NOT fit a standard Weaver rail and when you try and spring them open to fit, they snap like a dry twig. After that happened I hit a gun shop near work and picked up a set of Weaver medium rise clamps which aren't as pretty as the Burris mounts but they actually fit.