high Im building and 1885 high wall in 45-70. I am working on the extractor right now. I have the barrel cut and the extractor fit and operating but I am  wondering how to go about cutting the recess for the shell rim. anybody have any good recommendations?  I have thought of fixturing it in the mill and using a end mill to do this cut or installing it in the rifle and using the chamber reamer. but both of these have inherent problems at least in my mind. namely catching a tooth and ruining the extractor or making the chamber egg shaped.

I agree with SSDAVE.  Use the mill.  I tried using a finish reamer once and wound up running a reamer.