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.
How many man hours are consumed (wasted?) by handloaders meticulously weighing charges for typical deer rifles and shots inside 300 yards?
Mathman, Wasted......is pretty subjective! For those that enjoy.....the payoff is much like any other hobby. You throw money at it! But if 300 yards is the reasonable/ likely shot....then let’s consider. A few dollars, and a little time can convert a 2” at a 100 yard rifle to a 1” rifle. The 2” @ 100 rifle, then becomes a 6” (likely) group at 300 yards, under the best of conditions. Now throw in, that
most shooters from field positions are likely to triple their 100 yard group at 300 yards. There are, obvious, exceptions to my assumptions. If the “planets are aligned against the hunter) a deer at 300 could very easily be missed or wounded. The odds of a miss/wounding are substantially lowered with the 1” rifle, all else being equal! My math may not be perfect.... but I bet that it’s realistically close! memtb
