the most consistently accurate load I found for my marlin 45/70
was the nei bullet below sized .459
cast from 95% ww alloy and 5% tin
Winchester or federal standard rifle primers
45 grains of imr4198
easy 1"-1.2" 100 yard ,three shot groups of a good bench rest at 100 yards
its was consistently accurate , if the barrel was anywhere close to clean,
and it was deadly on deer and elk.
http://www.neihandtools.com/catalog/index.html
saco makes a similar mold
https://www.midwayusa.com/product/10...nose-gas-check