I cast that same bullet in a LEE mold. They are .457-8 and I size them down to .451 for the White. As for the 70 grains, I would have weighed 70 grains. My understanding is in the old days their powder for their 45/70 was a weighed charge and not a volume charge. But I will be interested in seeing your range results. I always liked that rifle ever since Quigley Down Under movie.