Hey Fred, thank you.

I suppose I could try a different die.  I had two shell holders, both produced the same results, so I sanded one and mic'd the edges to make sure I was "flat".  That produced a shell that was pressed further into the die and perhaps moved the shoulder a little, but not completely, and not enough to chamber easily.  Annealing, and the running through the die produced a case that chambered easily.  Without annealing, the cases didn't want to chamber easily.

If I recall correctly, I think I DID chamber a round after annealing but before reforming and even that action was easier than prior to annealing.

Maybe the last thing to try is just get some brand new R-P brass and try to chamber it, and even try to full length size it before firing and see if there's resistance at the shoulder.

I think (and I may be wrong) this is just an example where my rifle chamber is deeper than the carbine chamber and the fireformed rifle case is just that much difficult to get back to "stock" chamber spec.  If I'm wrong, I'm all ears.   :)