I have a box of those win. 777 primers to, I tried them in 3 TC inlines and one Knight they gave me vertical stringing on all the guns with all the loads I tried.
Good to hear from a shooter who had an experience like mine with those Winchester 777 primers. They left a lot more residual crud in the barrel than the Winchester 209 primers that i normally use. There was no crud ring, just a lot of crud for the full length of the barrel. Today when i switched to the regular Winchester 209 primers the sabot loaded much easier with a dirty barrel.
Several years ago i was using Pyrodex and tried most popular makes of primers and chose the Winchester shotgun primer. Been using them ever since except for some trials of Winchester 777 primers and 777 powder. That was a wasted effort.
Tomorrow i will stop in Duncan and get some more Winchester 209 primers.