Rick the 550 is a manual progressive and the 650 is a auto-progressive . They both rely on a powder measure to deliver the powder to the case . I like to measure each charge so they don't work for me . For that reason I use a RCBS rockchucker which is a single stage . Sorry I got my why before my what , but I think you will understand what I'm saying . I have owned both of the Dillons a 550 & 650 and still have a SquareDeal-B for pistol ammo . They are great presses but just don't suit my way of loading . Do you smell something