I got my 20T supplies from Todd Kindler, dies and his brainwashing materials (Terrific Twenties and Sensational Seventeens). I also got his wooden stand to attach my Forster Coax to. He has anything 17 or 20 cal related in stock.
Back to the topic at hand, one year ago I started reloading 204R then I got a 20T barrel for my savage 12FV. 20T is easy to form/make I don't have the patience for alot of steps. I got the form/trim die and the Redding FL die. I bought 2500 pieces of once fired, cleaned, deprimed and swaged Lake City from Brass Bombers. I decided to size brass in two steps using the form die then the FL die. I did form some of the once fired 223 in one step but I was getting more dimples in the case shoulder. I still loaded and fired without incident cases with dimpled shoulders. Moral of the story is either way works on once fired 223 brass and it's NOT tedious or difficult. I'm sure new 223 would be a little easier. I shoot 39gr Sierrs's at 3800 with 8208XBR and a Rem 7.5, lots of fun in the PD patch!!!