I too have some trouble with my iron sights on my sidelocks but I came up with a solution that really helps and is cheap and use it on all mine except the one with the fiber optic sights.
What I did was lightly file the front brass bead and applied a couple of light coats of my wife's white finger nail polish. On the rear sight, I degreased it and masked a narrow line (about 1/32") at the back of the sight in the center of the U notch and put the polish on.
I simply set the bead on top of that line. Works great in low light too.