Your 50-70 analogy is excellent.
Like I have been saying, about 85 grains of powder for the 295 grain PB is more than enuff. I wonder what happens to the 50-70 shooters bullet if he pumps up the powder charge to 50-150 and puts a humongous hollow point on the end of his bullet? I think the only practical diff between your plains hunter's bullet and the PB is the hardness of the lead. I always thought they were too soft. Others keep telling me they are too brittle. I don't know which it is, I just know the end result.
Being kind of a macho guy myself I understand people wanting to pound their chest and brag about how hot their loads are (funny though, some of the same people cry like a schoolgirl if their sabot is too difficult to load, go figure). But, with a M/Ler there is a point of declining benefits when it comes to too much powder. With my Encore and 250 grain shockwaves, that point appears to be about 110 grains of 777. Maybe with a different bullet I could get a hotter load. But, as long as I use common sense and stay within the limitations of where the gun performs, I get excellent results. If I got caught up in the escallation of "my gun shoots 150 grains of..." " aw man, mine shoots 175 grains of....." and super macho man "heck ya'll are wimps, I shoot 250 grains of ....." I would find that my results would not be nearly so good.
Hank