I have never owned a 77-22 but worked on a few in my 'smithing years. Actually very few, they don't give much trouble. With a little Dremel work to cut the left hand extractor slot, a 10-22 barrel will fit so premium barrels are available. As mentioned, LockTite on the barrel shank removes one variable.
Besides the second extractor slot the shoulder needs to be set back as well.the shank length on the 77/22 is about a 1/8” longer than a 10/22. I don’t recall the exact length difference but you get the idea.
