I sold all my big boomers and now only shoot 20 VT. Currently my powder of choice is RL7 at 18.5 grs pushing a .32 gr Vmax. Both of my VT's are Pac-Nor barrels in 11 twist. I have read good reports on AA2200 powder as well. I have used H4198, but get tired of running it through a drop tube. H4198 has the long pencil style of powder. Many people don't use a drop tube for H4198, but I always seem to have an issue with it. So I use a shortened drop tube that I use to use for black powder. I throw the powder light and trickle up. I know that I have the same charge in each round.
I make my 20 VT brass from 223 brass. It is a long process the way I do it, but my results have been very good in the field and on paper. You can use 221 Fireball brass and many folks just run it through the sizing die.
I use redding dies. When I first started loading for the 20VT, I used the RCBS dies. I had never used the spindle type of die RCBS makes and immediately stripped out the spindel since I didn't have it tight enough.
I spend way more time on my reloads than other folks I'm sure. After shooting bench rest for several years, you tend to really watch everything you do closely when reloading.