Ask ten people and you'll get ten replies. The "best" powder is what your rifle likes best. I looked in Ken Water's Pet Loads. IMR-4831 showed up a lot. I personally like Reloder series. I suspect RL-19 or RL-22 would be in the right range.
Basically, you've got stick, ball, and flake. The stick powders like IMR's tend not to be temperature sensitive. Long sticks can be harder to load with powder measures. Newer SC (short cut) powders tend to offset that problem.
Ball powders load and meter very easily because they flow well, but sometimes are temperature sensitive. Hard to light when it's way cold and may build excessive pressure when it's hot.
I used to worry about ultimate knock down. After I figured out that no rifle actually knocks anything down and it really doesn't matter how fast the bullet is flying when it goes out the off-side of what you shoot, I became more contented. Plus or minus 100 fps isn't worth ruining your rifle and/or your self.
