Can you use hodgdon new magnum pellets in the knight bighorn rifle?
As long as you have the 209 ignition, I would think it woud be just like any other Knight. I would say yes, as long as your rifle is new enough to recommend magnum charges.
777 Pellets were never designed to be shot in #11 ignition rifles, and need a hot 209 primer for best ignition. The Pyrodex Pellets on the other hand have a small amount of real Black Powder bonded to one end to aid ignition, and work fine in #11 rifles.