Lyman 49th gives 12 powder choices for loading the Sierra 125gr HP/FN bullet. I have loaded these up with W748 and TAC (Tac's data is available for free on the Ramshot website).
I had my best results using TAC. A Max charge of TAC was pushing the 125gr bullet at 2526 fps out of my 20" Marlin 336. Everything I've read about the bullet says it does a great job on deer, the only downside is the low BC means it can be pushed by the wind pretty easily. It grouped around 1.5 - 2" at 85 yards for me. Not as good as 160gr LeveRevolution bullets, but good enough to use for hunting. Point of impact is higher than other weight bullets. Even higher than the 160 FTXs.
The other item for consideration, is that this bullet is designed for the 30-30 and it's velocity range. If you load a different 125gr bullet that is intended for 308 or 30-06 velocities, it may not perform well when the velocity is dropped by 400+ fps in the 30-30.
