In most factory loads the 450 holds a big advantage over the 45-70 because of pressure limitations on the 45-70. However this low pressure limitation can disregarded in modern marlin rifles. As a hand loader the 40-70 can actually be loaded to slightly higher velocities than the 450 due to a slight capacity advantage. This is why in premium ammunition such as buffilo bore the 45-70 is slightly faster than the 450.
