As others have said, the H & R will handle Marlin level loads. Having said that, one does not need thermo nuclear loads in 45-70 to make them effective in the hunting field. I use a Rem. 405 gr. JSP
on top of 32 grs of IMR 4198 in my Handi rifle . It makes about 1350 FPS from my 22" bbl., and has proven to be a quick stopper on our large, corn fed bodied whitetails. It leaves an ample exiting hole, providing easy to follow blood trails. I would not hesitate to use it on elk, bear or moose. This load would likely would be at least 1450 FPS from his 32 " barreled Buff Classic.