I have a SDB setup in 9mm and want to buy the stuff needed to change over to reload .45. What else is needed besides the caliber conversion? Is the quick change kit or toolhead assembly necessary?
The quick change set or extra toolhead are not necessary but HIGHLY recommended. You won't have to mess with your 9mm setup and it's easier to change out with each caliber on it's own toolhead.
The SDB is best used as a one cartridge loader, from what owners say.
I would certainly get a toolhead, primer conversion kit, and possibly an additional powder measure if you have an existing load for the 9x19 that you load a lot of.