A buddy of mine has a M95 Marlin with 18-1/2" bl. He's using 49.0gr. Re#7 with a 400gr. Barnes .032" jacket Flat nose. It is listed in Speers manual with their 400gr. as being max at 28,000CUP and delivering 1,828fps. His rifle delivers an amazing 2,004 to 2,007 fps with this load, yet shows absolutely no signs of developing excess pressure. In his rifle, it is a good powerful working load. This is the same ballistics as shown for the .457 Wild West magnum's 2.2" case. In a 22" or 24" M95 barrel, this velocity should easily be achieved, showing the 1/10" longer case just isn't needed. (unless you are selling something)
; For even deeper penetration, the Speer 350gr. bullet, developed for deep penetration in a .458 WinMag can be sued in the .45/70 Marlin for in excess of 2,100fps and probably 2,200fps as shown for the 2.2" case. The crimp groove is nt placed properly for use in the Marlin, so the bras needs to be shortened slightly, .165" to 1.935" in length. This will not change the ballistics nor the capacity over normal 400gr. bullets as the base of the bullet comes to the same depth in the case AFTER shortening as the 400gr. bullets take up normally. This, I have measured out to be correct. It is one possibility for the round. On the other hand, the 350gr. Hornady FN or RN as I used, at 2,270fps in my .458 2", penetrated a Moose's skull & brain, then 3 vertebrae and exited 1/2 way down the Bull's neck. The range was 95yds, showing the 350gr. RN Hornady to be a tough bullet as well, and suitable for normal loading in the 2.1" case.
: I just don't believe the extra 1/10" is necesssary, nor does it actually benefit the Marlin. What this all comes down to is using the proper powder and Reloader #7 seems to be the one for sue in the Marlin. The picture below shows a 350gr Speer, whole and sectioned to show jacket thickness.
: For those who are impressed by numbers, my buddies load produces an approximate 2,020fps actual Muzzle velocity (+16fps for screen spacing at 20') for 3,624ft.lbs energy. As silly as these types of numbers are, an extra 80fps developes another 292 ft. lbs. for 3,916ft.lbs., yet makes no difference on the game being shot.

http://img.photobucket.com/albums/v638/DarylS/350gr.jpg