Abstract: A core lifter assembly includes a combination of a core lifter ring and a core lifter case. The ring has an axially extending portion of an outer generally frusto-conical configuration having an included taper angle ?. The included taper angle ? is also the taper angle of the outer circumferential surface of the ring. The included taper angle ? may in alternate embodiments be ?6°; ?7°; ?8°; or ?10°. In one embodiment an upper limit of the included taper angle ? may be about 30°. Thus in one embodiment the included taper angle ? may be expressed by the relationship: 30°???6°. Further, the angle ? may comprise any sub range within the aforementioned range of 6-30°. However in other embodiments the taper angle may exceed 30°.