I'd say for the 264WM the best bullet is the 160gr Woodleigh Weldcore, and it's not particularly close. Nothing else can match the sectional density/penetration while still maintaining a decent BC.
Load:
--------
160gr Weldcore
64.8gr Retumbo
Nosler brass
Federal 215 primer
Lee FCD crimp slightly over 1/4 turn
0.02" to lands
Velocity averages 2910 out of a 24" Winchester.
Accuracy is plenty good.
