I had a 20 Practical built on a PTA and a 26" Criterion that was the best shooting gun I've ever owned. It was so accurate it got boring, sold it like an idiot.
I used a 223 Redding type S bushing die with the proper bushings to neck down 223 brass to a 204 neck. I used two bushings to initially size the cases and then the final bushing to neck size fired case. For seating I used a Hornady 204 ruger seating die. Worked great- I'll try to dig up some specs and pm them to you but if you want an amazingly accurate round that has basically no recoil and will take pds out farther than you would believe than this is the round for you.
The difference between a 20 Practical and a 20 "Tactical" is 2 things- the "Tactical" changes the shoulder, an extra step that serves absolutely no purpose, and the 20 Practical doesn't have that godawful stupid name. The 20 Practical is just a 223 necked down to 204, and it is awesome.
Wish I still had mine.