Big Game works very well with a wide variety of bullet weights in the .257. My wife used enough BG with the 115 Berger VLD in her NULA Model 20 to get 2900+ fps (can't remember the charge right now) in New Zealand a few years ago to take a bunch of feral goats and a fallow deer.
Hunter also works in the .257 with any bullet weight from 100 grains up. My wife mostly uses 47.0 and the 100-grain TTSX as the all-around load in the NULA. It gets right around 3150 fps and is quite accurate, and she's taken a pile of western big game with it--pronghorns, whitetails, mule deer and one cow elk.
Magnum works too, but in my experience it's best with 115-120 grain bullets. Basically you fill a case with powder and seat a bullet! Velocity is 2900-3000, depending on barrel length and the particular bullet, and accuracy usually very good.
