I am assuming that a set screw holds the shell holder in place with this press and that the shell holder is not held in place via a spring clip as with my other presses. I just picked one of these up, slipped a shell holder in the slot and found that it did not "snap" in as I expected but I did find a set screw on the shaft and that seems to work.
Would love to hear from other Spartan owners and what they think and how they like this press.