I haven't tried the Win 777 primers, they were sold out last year when I went looking. What I did find & buy was the Remington BlackPowder Kleenbore primers. Only used a dozen so far - did most of my other sight-in & shooting with regular Win 209s. Everyone of the Remingtons has worked just fine, no misfires out of the few, so far.
Remmys aren't the first I reach for in 22 lr ammo because of misfires.
And I sure wouldn't recommend Rem to anyone right now because of the time it's taken to get my Handi back with some new barrels, but the truth is the truth. Did not have the crud ring like the regular Win 209s put in the bore either.