Have about 50 .348 cases formed and trimmed to .44-77, but the rims are .076-.077 and they will supposedly fit the Shiloh chambers, but not the C. Sharps chambers, which take a thinner .067 rim. This must have been the reamer my gunsmith used. So I need to find a "cartridge machinist" who can uniformly shave .01 off the forward edges of the rims on these cases. Anyone out there wants to raise their hand or direct me to a good source for this work?

If you have a drill press with a large enough chuck, you can use a file with a safe edge to do it yourself.
Not too difficult.
I'd do it for you but my lathe is a little too loose to do such a job without the rifle here to check each cartridge as I go.
Peeling off .01" reliably would require a lot of small cuts and a lot of measuring with the mic to be confident that I could send them back to you in the condition you want.

Thanks Huvius. I just can't imagine myself doing a neat job on 50 cases with my drill press. I couldn't even color inside the lines in first grade.
An alternative is to wait for Starline .45-90 brass for a usable workaround.

NO do not drill them. Send them to me. Which should have been your first COA.

I have a 600 Nitro Express rifle, and the available brass wouldn’t fit in it.

Rims too thick.

I turned them down in my lathe.

Fellas, I must sheepishly confess now that after comparing the cerrosafe chamber cast with the cases I bought as .44-77s, it became clear the shoulders did not match. I had been focusing on diameters rather than longitudinal measurements. Once I slipped a couple of cases into the .43 Mauser full-length form die, the shoulder location was a much better match, and case mouths, too. They now chamber just fine, and I will be careful to neck size only once fire-formed.
No fool like an old fool ...
Saeed, the thick vs. thin rim thing used to be a fairly common issue with some of the classic big-bore cases when the Brits started going from black powder to smokeless. I wonder if that is what was up with your .600 brass.