Lyman .515" diameter 340 grain, bullet mold, single cavity, steel blocks only for 56-50 Spencer. Remember Spencer put the powder charge first (56) and caliber (.50) second, the opposite of most other cartridges today.
These precision mold blocks are made in the U.S.A. and tend to cost a bit more than other brands. They are nice quality. Special steel alloy mold blocks hold heat, for even casting temperature. Steel blocks almost never wear out, if properly stored. Blocks are made in one size, cut with a single cavity for large bullets. Mold handles are sold separately. Use large Lyman handles on all current production molds.
Also order #LYMAN-HL large mold handles, or #LEE-HANDLE commercial mold handles.
Also order #LYMAN-TP-141 Lyman Top Punch #141 for your Luber Sizer press.