Miller, the Ideal doesn't have reversible pins. My Bridgeport 12 does, but I don't see how its done. I see no way to change it. My 12 gauge loading block is homemade with a spade bit and scrap lumber. Do you see any practical difference between the flat and rounded crimp? While these tools preceded plastic hulls, what difference would have it made on the paper shells? It seems to me that the flat top on a modern plastic hull would eventually stress the plastic more than the round crimp. Gil