Fred, I appreciate the time responding! 

The cases were a mix.  The R-P had been loaded previously, but I do NOT know how many times.  I doubt many.  They were a gift with the rifle from a dear uncle.

The Winchester cases were from a box of ammo that was fired once (some in the rifle, some in this carbine), then resized this time to reload.

I had the same issue between the RP & Winchester - but ONLY the ones that had been fired in the rifle first.  For example, a new in box winchester round that was fired in the carbine then sized and chambered in the carbine easily.  the Winchester or R-P that went in the rifle first, then in the sizer, then in the carbine just didn't want to go.

It's ENTIRELY possible that due to difficulty in sizing those rounds (the rifle fired cases) that the sizer didn't push the shoulder back to a factory spec.  Once softened, however, the sizer easily pushed them back to spec and they chambered in carbine without pause.

I suppose this may be moreso an issue with the rifle having a deep chamber than the carbine having a short one... :-)