Doug,
A top punch is a separate part that goes into a lubricator/sizer and fits the top of the lead bullet, and pushes the bullet into the sizing die. For sizing a given bullet, you need a die of the appropriate diameter, and a top punch. If you don't have the exact top punch for your bullet, you can put a dab of epoxy into the recess of a punch of the approximate shape, then lightly push a bullet into it until the epoxy sets up. Release agent on the bullet tip, of course. I believe RCBS and Lyman top punches interchange, but SAECOs are unique. Hope this helps.
Paul
