Type metal doesn't actually expand much when it solidifies either; it's an alloy of tin, lead, and antimony which contracts when it solidifies, but only very slightly. Antimony by itself expands when it solidifies, and so by varying the amount of antimony (and consequently the proportion of antimony crystals in the solid) you can get a type-metal-like alloy that expands when it solidifies, one that contracts, or one that remains precisely the same size. What you actually want is something that contracts by the same amount as the mold, which is a very small amount, because the mold ("matrix") is made of iron.

The Sn–Pb–Sb eutectic is 4–84–12. Most type metal alloys have a substantial excess of antimony over that.

https://en.wikipedia.org/wiki/Type_metal