"Is there a simple and inexpensive way of doing this without buying into special equipment?"
"I've got a dial gauge, V-blocks ... Seems to me some clever arrangement of this equipment should do the job"
You have the basics of the "special equipment" in the dial indicator and blocks. Goggle the Sinclair International site and find their concentricity gage for further ideas. But the case trimmer won't help, the shaft-to-collet alignment isn't sufficently concentric or rigid for that work.
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