This is the Sinclair case neck thickness and variance gage that sells for about $30 without the dial gage. I'm not referring to the
Sinclair $90 concentricity gage which I already have.

Sinclair doesn't make a 20 cal pilot for this neck checker gage. But I was told that I could slip the case directly onto the spindle without a pilot, and the spindle itself will hold the case firm.

This is an after the fact discovery with this tool that is reported to just happen to work, and I'd like if somebody here can tell me if they have done this with their 204 or 20 tac cases before I order the tool. If the case is going to fit loose or sloppy on the spindle when you spin the case, then I'll pass on it.