If you're not happy with the accuracy of 3D printing, and the materials aren't working for you either, why not go with CNC milling for your horseshoes? It doesn't seem that you really need the ability of 3D printing to produce undercuts and interior volumes, which is the major reason for using it on a prototype. With CNC you could cut it out of steel and just weigh it if you needed to know the mass, or measure the volume with Archimedes' method.