Some words of warning.
ABSOLUTELY do not believe any of the .45-70 loads posted on the net until you've checked them against a current reloading manual.
In another website, it is suspected that a particular shooter purposely posted loads that would be dangerous in a Marlin 1895. His idea of a sick joke.
Then there's the guy who exceeds the maximum listed in a recent reloading manual and doesn't blow up his gun, so he figures it's safe in ALL Marlin 1895s.
Not true! Each rifle is an individual with its own strengths and weaknesses.
For example, the oft-quoted load of 53.0 grains of IMR3031 under a 405 gr. jacketed bullet --- as proposed by the late gun writer Elmer Keith --- is beyond maximum in my own Marlin 1895 of 1977 manufacture.
About 20 years ago I foolishly made up a box of such loads. After a few shots, and after seeing the distended cases and flattened primers, I pulled the bullets on the rest of the box and started over.
Never again have I used a load without checking it against two reloading manuals printed within the past five years.
Lyman's 47th reloading book (circa 1998) lists 48.0 grains as MAXIMUM in the 1895 Marlin and 1886 Winchester. So, I was using a load 10.4 percent higher than Maximum!
Forget what Joe Blow says about the reloading companies being conservative in their load recommendations.
The fact is, the reloading companies that publish the manuals have access to state-of-the-art equipment for measuring pressures. Few reloaders do.
And I suspect that if ALL reloaders HAD access to a lab to measure the pressures they generate, they'd quickly reduce their charges.
The .45-70 is a grand cartridge but it was never intended to be a "weak .458 Winchester Magnum" as some people are trying to make it.
What little extra velocity you gain will not be noticed by the game but it WILL strain your rifle and make it wear out sooner. Heck, it might even let go.
Which brings me to another point: Just because your rifle holds together after 5, 20 or 100 "hot-stuff" rounds doesn't mean that load is safe. It may take more than 100 rounds to eventually weaken or damage the gun.
Frankly, I can't see why everyone's in a race to throw heavier bullets faster in the .45-70. The fact is, the factory load with its 405 gr. softnosed bullet at 1,200 to 1,300 fps has reliably killed game for over a century. The same may be said of the 300 gr. jacketed bullet.
Once about 1,200 fps is reached it isn't so much the speed of that fat, 300 or 405 grain bullet that kills game, it's where you PLACE that bullet.
Enjoy that Marlin. It's a great gun and should amaze you with its accuracy. Mine has for more than 25 years.