Go back in time and you will find the 6x47 was a popular benchrest cartridge. Remington even chambered their 40x rifle for it.
At that time the 222 case was necked up to 6mm. The PPC cartridge was created by 2 shooters with names of Pindell and Palmisano.
Within a very short period of time all the other then popular benchrest cartridges were obsolete. There were 2 versions, a 22 and a 6mm.