Yes, powder charge and the distance the bullet is off the lands.
I generally start at .030" off the lands and seldom have much reason to change that.
Modern temperature compensated powders are much better. With some older powders, a change of 30 F in barrel and ammunition temperature is equivalent to a change of 1 grain of powder. So trying to fine tune those down to .1 grain is an exercise in futility... unless, of course, your are controlling temperature down to plus or minus 3 degrees F.
I don't shoot 7mm Mag, but I suspect that a 160 grain Partition over Retumbo would be a winning combination. Somebody that has actually tried that combination can give you a better report than I can.
There are a multitude of ways to do it right. Enjoy the trip.
Last edited by denton; 06/18/18.
