Well first off, I think that when one starts considering 20VT, TAC20 etc... that is not the only gun in the cabinet. It is based off of want more than need. The main draw is velocity, component economy/barrel life and terminal ballistics. The Tactical 20 was invented by Todd Kindler long before the .204 Ruger hit the market. Based on the .223 Remington parent case, the Tactical 20 is simply the .223 necked down to 20 Caliber with a 30-degree shoulder. Some versions have slightly less body taper as well--it's wise to compare reamer prints. Although the Tactical 20 has about three grains less case capacity than the .204 Ruger, it delivers very similar performance. With the right load, you can get Max velocities with 32- and 40-grainers that give up little or nothing to the .204 Ruger. Varmints probably won't know the difference. The Tactical 20 is easy to load and exceptionally accurate. Currently, Cooper Arms of Montana and Dakota Arms offer factory rifles in Tactical 20 chamberings.
Most of this did not come from my mouth, but from
http://www.6mmbr.com/20caliber.html
Since the Tac 20's parent case is the ubiquitous .223 Remington, there is a huge selection of high quality brass available, limited only by your budget. Some precision shooters like to start with Lapua brass. The author has had excellent results using IMI brass, which is strong and very durable.
Forming 20 Tactical brass is generally a two-step process. You start with a 223 Remington brass that has been full-length sized in a .223 die. Then run the brass through a Tactical 20 forming die, and finally run it through a Tactical 20 full-length die. Case lubrication/wax should be used very sparingly just on the neck and the body. Too much lube will result in wrinkled shoulders. Although the wrinkles will blow out once the case is fired, they make the cartridge looks somewhat unattractive. The author has had great results using Redding dies with Hornady Unique Case Lube, while others prefer Imperial Sizing Die Wax. The Hornady Unique Case Lube is a little thinner, so it tends to be more forgiving if too much is used.
Some reloaders, like the author, will anneal the brass as the final step. Although not necessary, annealing tends to help the fire-forming process and extends the life of the brass a bit.
I was originally thinking of going with the 20VT as well but decided on the TAC20.
TACTICAL 20 LOAD MAP
Bullet GR Maker Powder Charge Primer Case Velocity Barrel
Twist Comments
32 Hornady
V-Max H4198 23.5 CCI 400 IMI 4000 Lilja 1:12 K. Hamzeh, Form Load
32 Hornady
V-Max H4198 24.1 Rem 7? IMI 4175 PacNor 1:12 MontDoug Load
32 Hornady
V-Max VV N133 25.2 CCI BR4 IMI 3950 Wilson 1:12 A. Clark, Accuracy Load
32 Hornady
V-Max H322 27.0 Rem 7? IMI 4240 PacNor 1:12 Dan C. Load
32 Hornady
V-Max Reloader 10X 25.5 Rem 7? IMI 4155 PacNor 1:12 Dan C. Load
40 Hornady
V-Max Benchmark 25.6 Rem 7? IMI 3900 PacNor 1:12 MontDoug Load
20 VARTARG LOAD MAP
Bullet GR Maker Powder Charge Primer Case Velocity Barrel
Twist Comments
32 Hornady
V-Max H4198 18.7 Rem 7? Rem 3780 PacNor 1:12 MontDoug Load
32 Hornady
V-Max VV N120 17.8 Fed 205m Rem 3715 PacNor 1:12 Dan C. Load
32 Hornady
V-Max IMR 8208 19.4 CCI BR4 Rem 3760 Wilson 1:12 D. Moore, .3 groups
32 Hornady
V-Max RamShot TAC 22.0 Rem 7? Rem 3600 PacNor 1:12 Dan C. Load
32 Hornady
V-Max H335 22.4 Rem 7? Rem 3770 PacNor 1:12 Dan C. Load
32 Hornady
V-Max Reloader 7 18.5 Rem 7? Rem 3705 PacNor 1:12 Dan C. Load
32 Hornady
V-Max AA 2200 20.5 Rem 7? Rem 3800 PacNor 1:12 Dan C. Load
32 Sierra
BlitzKing VV N120 17.6 na Rem 3750 PacNor 1:11 Dean's Savage Load: "Love the cartridge."
35 Berger FB VV N130 19.3 Fed 205m Rem 3512 Pence 23" Most Accurate (.304") N130 load for AccurateReloading.com
35 Berger FB Reloader 7 19.3 Fed 205m Rem 3675 Pence 23" Most Accurate load (.269") for AccurateReloading.com
35 Berger FB H322 20.6 Fed 205m Rem 3511 Pence 23" Best H322 load for AccurateReloading.com.
35 Berger FB H4198 19.2 Fed 205m Rem 3650 Pence 23" Accurate Reloading.com
3723 fps with 20.0 gr H4198.
RUGER 204 LOAD MAP
Bullet GR Maker Powder Charge Primer Case Velocity Barrel
Twist Comments
32 Hornady
V-Max H4895 29.1 Rem 7? Hornady 4175 Savage 1:12 Hot Load
32 Sierra BlitzKing Benchmark 27.9 Fed 205m Hornady 4000 1:12 Sierra Load Map
32 Sierra BlitzKing Reloader 10X 26.5 Fed 205m W-W 3900+ Wilson 1:12 K. Lunde Accuracy Load
32 Sierra BlitzKing H4895 28.5 Rem 7? W-W 4005 Savage 1:12 Silverfox
35 Berger FPHP H4895 27.4 Rem 7? Hornady 3900 Savage 1:12 Silverfox
39 Sierra BlikzKing Reloader 10X 24.8 Rem 7? W-W 3805 Savage 1:12 Silverfox
39 Sierra BlitzKing AA2520 27.4 Rem 7? W-W 3845 Savage 1:12 SilverFox
39 Sierra BlitzKing XMR 2015 25.6 Fed 205m Hornady 3600 1:12 Sierra Load Map