My understanding of the Precision Rifle Series is that its a clearing place for several venues conducting Precision Rifle Matches.
The idea is to list all (or as many as they can find) matches in one spot so shooters can be made aware of the PR matches out there.
If I remember correctly, the PRS also tried to come up with a uniform scoring system to get everyone on the same sheet of music but I don't think that panned out well as various matches are so different it would make uniform scoring impossible.
There is no governing body (such as the NRA or CMP) to standard the rules. Too many variables.
An Example:
Smith PR INC. Has a 900 yards range. Do to the type of targets magnum rifles are not allowed. Targets are at different ranges, no laser range finders allow.
Jones PR INC. Has a 1400 yard range, Rifles up to including the 338 L and 50 cal pr rifles can be used, as can laser range finders.
Also some matches require two man teams, others don't.
As you can see, a uniform scoring system would be impossible without a rule book bigger and more complicated then the IRS tax code.