Not to be a smart butt, but fast enough to kill a deer...
I shoot 80grs FFF Goex in my Knight behind a 300gr .430 Hornady XTP and my hunting buddy shoots 85grs 777 behind a 240gr .430 Hornady XTP...We both kill deer, can't really tell much difference except I seem to get more pass throughs...
More powder isn't always the answer as both these rifle's groups start to open up with 85grs and just get worse after that...