Read some great info about the 20 cal's over at accurate shooter and thought i should share it.
http://www.6mmbr.com/20Caliber.html
A great opening paragraph
Treatise for Twenties by Kory Hamzeh, 6mmBR.com 20 Caliber Editor
Why are folks turning to the "Terrific Twenties"? Among the most important reasons are: low recoil, high velocity, low noise, reduced cost, longer barrel life, and better ballistics for a given bullet weight. In short, compared to a .223 Rem, a Twenty shoots flatter, costs less to shoot, and is easier on the shooter's shoulder and his barrel.