Wilson makes everything themselves, I personally saw every part being made at some stage of production when I visited. They have large pallets of rough forgings that they turn into gunsWhere do the semi-custom 1911 builders like Wilson Combat, Ed Brown, Guncrafter, Nighthawk, and Les Baer get their frames and slides from? Do any of them machine frames and slides from solid chunks of metal?
I saw short video on Les Baer's shop. It didn't show machines capable of manufacturing frames & slides. I'm suspicious he procures them from a company that specializes in manufacturing frames and slides.
I know many small makers get their slides & frames from Jen or Caspian. I'm sure there are many makers of them.
I was looking at some STi and Caspian slides I have around and compared them to an old 70s produced Colt. The Colt slide had very rough machining internally, with surface finishes exceeding 125 RMS and in some places in excess of 200 RMS locally. The recently made STi and Caspian slides had surface finishes that were smoother than 63 RMS in most surfaces. Some of the better modern examples are much better machined than those of a few decades ago.