Done.
Tools I picked up for the cut:
Nelson bastard file, Dewalt 32 hack saw blade, cheap HDX hack saw, cheap miter box (didn't use much), wood door shims (awesome), Birchwood bluing paste, Dewalt mini clamp (didn't use), HDX deburring tool, and BESSEY vice (didn't use-impossible to get the rounded barrel to stay on).
Observations:
1 The 500 rib is defiantly steel and defiantly held on to the barrel at each rib,
2 The rib acts as a near perfect horizontal level whereas all areas of the barrel acts as an impossible plane to level.
3 The poking out nut on the barrel was the project's unexpected difficult item for holding this steady=what a pain that was to figure out how to level,
4 The bastard file is leaving a texture in the practice cut. I may get a smooth file for the last few sweeps,
5 The cutting took a bit of time, yet went faster than I thought it would as I was doing it. Weird.
Started with a practice run using the last rib before the muzzle. I held it entirely by hand against my work bench . Went well, but my cut meandered and was much thicker at the bottom. Oops.
Next I graduated to the real cut. I used wood door shims to prop up the muzzle end in the miter box. Using a small level on the length of the rib, I leveled the barrel with the shim and held it all down by hand. I am not sure if the miter box did much. Cut away.
I am going to clean up it all up and hit it with the blue. Patterning to follow.
Thank you all for your tireless answering of my repeated questions. It was defiantly easy. Not easier than I thought, but easy.
Sorry for the photobucket. Didn't realize how crappy that got.
Practice cut:
Half way done:
Fin with all three barrels: