I've loaded quite a bit of BL-C2 over the years. Mostly when I shot it out of a 7mm/08. I don't have any experience loading the 7x57 with it though. Good luck.
Shouldn't be any real difference...
BLC-2 is a decent powder for the 7mm Mauser...
of course there are others than might be even better, such as H 414....but I still wouldn't feel handicapped expecting a 154 grainer at 2500 fps....
and yeah, I've used BLC.2 out of several 7mm Mausers.. along with H 380....and a host of other powders from older reload data...
