I've worked up a couple of 204 Rugers. Kind of like them, lots of performance, but I think they run a little hot for me. If I do a 20, it will be either a TACtical, or maybe a VarTarg, the former most likely.
If you do a Tac20, I'd HIGHLY recommend Greg Tannel's method of chamber reaming. Kindler's
reasoning of bumping back the shoulder of the .223 case makes no sense at all. IIRC, he
bumped it back .010". Go ahead and ream the chamber so that the cases need no bump back
at all, so that the die only sizes the neck, just as in the 20 Practical.
In my experience, no need to fire form the cases with squib loads, just go with the lower
recommended loads. They are just as accurate as loads in formed cases.
I had a barrel done with the shorter chamber and it just makes for more steps and little to no
more gain. Even at that, 24gr H4198 gets 32gr Hornadys to 4100fps with no pressures signs
in an Encore barrel. Accuracy puts my Ruger American Predator in .204 to shame.
