I've compiled a list six contractors located around the country who specialize in "prototype quantities" (single digits) that I have to send RFQs to once the frame is perfected. The contractor that was in River Edge NJ that @Sokramiketes used back in the day for his Z scale flat cars is no longer in business there.
These contractors work from digital masters so they will account for the shrinkage factor I'd imagine.
Yeah, Best-Cast was a loss. They were great to work with. Once they understood the dimensional accuracy was needed, they did two rounds of tweaking with me. Then we ran 100 copies. Brass casting seems to be a bit of a scientific mystery somehow... but it's probably just related to volume in 3 dimensions. Best-Cast was good at nailing ring diameters (they were a custom jewelry company) and then the shape of a Z scale flatcar was a new mystery!
I watch the Proto:48 folks and their expeditions in custom parts too. They're using burnable resin for prints and sending to a long time model railroad supplier in California. But frequently need a test batch or two to zero in on shrinkages.
