The same goes for a 44 mag and a 444 Marlin. Totally different.
This is partially true and partially not. Let me explain. While the 45 Colt fires .452, and the 45/70 fires .458 (or .460 with lead boolits and you don't want to lead your gun) the boolits are not interchangable, no way no how.
The 444 Marlin and 44 Mag bullets both shoot .429J/.430L but while the sizes are the same, the pistol bullets should not be fired in the 444 Marlin because the bullets are not built to handle the velocities generated by the 444. This would not be a problem with hard cast lead in the 444. All Marlins I've seen like fat boolits with lead so if to load for 444 I'd def go with .431
You can even get the microgroove barrels to shoot lead good if you size them fat.I'll tell you another thing, if you were to get a 45/70 do not shoot any cowboy factory loads out of it. Most if not all were sized to .457 and will have you cleaning lead out of your rifle for a week. Ask me how I know.