Is the M77 a true controlled round feed like a Mauser, or can a single round be loaded directly into the chamber? Also, is the bolt/extractor design the same between the original, MKII and Hawkeye models?
The 77 tang safety is push feed. A round can be added to the chamber on bolt closed. The 77 mark II will have current production being controlled feed but some of the 1st production runs were push feed. As far as the Hawkeye--- I do not know, I've never picked one up.
The M77s made since shortly after the Winchester M70 Classic went into production have been controlled feed rifles. Winchester got the commercial rifle craze for CRF rolling in recent times. (Prior to that, it was a lot harder to argue the virtues of CRF over PF because one needed a Mauser type action in order to make their case and the large commercial makers didn't replicate that action.) But the Mk II and Hawkeyes are CRF. However, as with about any commercially made rifle some function it this respect better than others. Many need some tuning to get them really running well - though they still work for ordinary purposes just fine as they are boxed in most cases. But any of the current Rugers will chamber a round either from the magazine or directly into the chamber by hand.