One of my planned projects is to make a matched pair of 1851 navy type revolvers. Most of the parts look fairly straightforward for me to machine, but the frame itself is perplexing. Namely the two large spherical radii on the back where the hammer goes. I could easily do this on a CNC machine, but due to a lack of access I have to do it manually. Any fellow machinists out there have insight on how I could do this manually? I know that's how they had to do it back in 1851.