“C” is just part of the identification in the serial number. The B and C’s are slick running actions for the most part.
The A, B, and C prefixes are all the “good” prefixes. The anti bind slot officially started with the A prefix around 1975 (but I have seen a late non prefix with the slot).
I’ve had several gunsmiths say the A prefix actions were the straightest, the lugs had the most contact with the action raceways, and the handles were clocked perfectly.