I am certain the RCBS shell holder will fit. The retaining spring in the Lee presses is pretty tight when new. The first time you insert any manufacturers shell holder in a Lee press it be a very tight fit. I have used several brand new Lee hand presses and they all were a tight fir for shell holders the first three or four times I inserted them. On one hand press I used pliers to gently squeeze the shell holder into the ram and then to remove it. Just a firm squeeze both directions. After that the shell holders insert and remove just as expected. I use several of the hand presses and I am pleased with them.
Call Lee.
