I have SDM gold beads on both my 629 and 625 Mountain Guns. The bead is slightly larger than the rear notch is deep, which presents a different sight picture when shooting fast versus shooting slow. Since fast double action is a close affair, it hasn't bothered me yet. I am, however, in a constant state of research and development! (And no, I am not very fast with either gun, but I have watched Mr. Miculek and know it can be done!)