45-70 loads are often divided into three groups. Old rifles, strong/modern lever actions and custom bolt actions. Marlin will safely handle the first two levels. .45 LC get a boost in the longer barrel but you can also use the Ruger, TC load data for the modern Marlin and Winchesters. These frames are set for .44 mag and 45 LC. If in doubt with your ammo check with the manufactures web site. If reloading then you will see how the loads are broken up. Marlins are some of the strongest lever actions.