Have found Hunter to work very well with 100-grain bullets in the .257 Roberts, but Magnum works better with 115-120 grain bullets. In fact I was once told by Doug Phair, the owner of Western Powders until it was recently sold to Hodgdon, that his standard load for 120s in the .257 was filling a case to the mouth with Magnum, then seating a 120 Partition seated on top.
Tried it, and it shot very well. In fact, Eileen used it for a while in her NULA .257. Muzzle velocity was around 2950 fps.
