It turned out that my RCBS .30 Carbine die set had the expander/decpaper combo die! In my die box I had a carbide sizing die also, so I replaced what I thought was the sizing die at some point, probably because the other size die didn’t work! RCBS is sending me the replacement decapping stem to use with the old sizing die.
When I talked to RCBS, they said that all their dies were made that way until they came out with their progressive press and they needed to combine depriming with sizing. I will need to check my other older die sets!