The 204 Ruger was first introduced on the 2004 SHOT show. It was developed together with Hornady. Originally it was loaded with a 32 grs V-Max bullet, firing at 4225 fps. The case has about the same capacity as the 223 Remington case. 

This text is based on information from “Cartridges of the World”, Hodgdon reloading manual, the cartridge designer and/or own resources.