Here are my loads that I use in my 1895G, and these are not as stout as they could be, simply because I like it mild, NOT wild. With the 45-70 it just doesn't have to be that way.
1.) 300-gr JHP Hornady bullet
2.) 405-gr JSP Remington bullet
3.) 405-gr FP Shooters Choice bullet
4.) 500-gr SHC Elk Buster
My Marlin 1895G loves all of these, and each has it's own intended purpose. The 500-gr Elk Buster will shoot end to end on bison and bust both shoulders of a very large bull elk.
All my loads average approx 1550 fps.