To provide a refractory metallic core to accommodate differential thermal expansion between a feed core and the refractory metallic core.

An investment casting core combination includes a metallic casting core and a ceramic feedcore. A first region of the metallic casting core is embedded in the ceramic feedcore. The metallic casting core includes a plurality of body sections. The first region is along at least some of the body sections. The metallic casting core includes a plurality of springs spanning gaps between adjacent body sections and unitarily formed therewith.