If you are just starting with a Dillon, suggest you just get a 550, it is the closest thing in simplicity and cost of change over, to having a single stage in a Dillon progressive. Were it me, if I could get one on the way, today, I would go on and get one coming. You can not go wrong if starting out with a Dillon to get a 550b or c. They are the #1 selling Dillon for a reason.

“To expect defeat is nine-tenths of defeat itself. It becomes a self-fulfilling prophecy. It is best to plan for all eventualities then believe in success, and only cross the failure bridge if you come to it."
Francis Marion - The Swamp Fox