Lost wax would get you a rough casting, but would still need to be machined to perfection.
I helped my brother-inlaw cast some fittings for an old scabbard that came out looking pretty good. Finished up with hand tools, gave them a nice polish and they looked great. There’s an article on the web somewhere written by a guy that actually made a brass lower using the lost-wax method. I think he hand carved or cnc’d his wax mold but it’s been too long and I’ve forgotten the details. I do know my daughter’s printer came with a low temp plastic meant to be used to print reverse/sacrificial molds for casting. And just think how cool a brass AR-15 would look!