The CPSA site explains it in detail but it works as so:
Every 3 months, the CPSA look back a year at each shooter to get their average.
AAA are the top 5%
AA are 5-15% (or 85-95% depending which way round you want it..)
A are 15-45%
B are 45-75%
C are the bottom 25%
So, the classification cut off points vary each period to fit the above. Currently AAA is about 88.3 and you need 75.3 to climb out of C class. All the lower classes are of course full of people progressing, hence they will always score above what “looks right”. But not for long as they will get promoted if they keep doing it..
Apart from major championships, AAA and AA compete combined as “AA” at normal reg shoots (which makes it bloody hard for a AA like me
)
The C and B class scores are the least predictable usually. Basically there is so much headroom if somebody has a good day. My mate won C at Westfield last week on 87, 9 clays clear of second. Looks totally wrong, but he’s a 20 year experienced shooter (was in A class years ago) who has been on shocking form, sometimes has health issues, but massively got it together on the day. The shoot also had mainly longer targets which he is best at. It’s VERY dodgy to expect B and C class scores to “conform”.