It would be interesting to measure the diameter of the pin on your die, then compare that size to other dies as well as to the Speer primer. I would bet they nest together with a nice compression fit between the two. Perhaps the Speer primer is different then the others you normally come across. THat plus the slicker nickle case alows it to suck back in rather then be pushed off. My Lee dies all have very rounded decaping pins. No square edges at all on the ends.
Ignore Text Size....posting from a phone.