Abstract: In accordance with an illustrative embodiment of the present invention, a perforating gun apparatus for forming holes in a well casing through which cement can be circulated includes a mandrel, four arm-mounted, shaped charge carriers on the body, and bow springs on the body in the plane of each carrier for biasing the carriers outward into sliding contact with the well casing. The charges form evenly distributed series of vertically arranged holes the casing, without damage to an outer casing string, so that cement can be circulated through the holes and into the annulus without channeling.