Abstract: A gun sight mounting assembly for a firearm having a vent rib on its barrel. The assembly includes a mounting base which has a sight member attached thereto. The mounting base has a recess which is adapted to tightly engage a width of a vent rib. A securement member is provided which may be drawn toward the mounting base for clampingly securing the vent rib therebetween for securing the gun sight to a vent rib.