I have a Marlin 1895 I purchased new in 1977.
Some years ago, I assembled 405 gr. Remington jacketed softpoints over 53.0 grains of IMR3031, in Winchester solid head cases with CCI Large Rifle primers.
This load was entirely too hot for my rifle. Cases were bulged and it was obvious I had entered a danger zone. :eek:
This same load is often found in the writings of the late gun writer Elmer Keith. I would not adopt this load straight across; work up to it.
Granted, lead bullets can often be driven faster, at lower pressure, than jacketed bullets because of their inherent lower friction. Nonetheless, I do not suggest you start at 54.0 grains of IMR3031. This may be an excessive load in your rifle.
I would suggest you start at 49.0 grains and increase the charge by a half grain each loading. Watch for excessive pressure along the way.
Each gun is an individual. What works in one may not work in another, and what is safe in one may be an loverload in another.
On a personal philosophy note:
I see little advantage in hot-rodding the .45-70.
A 405 grain bullet at 1,700 fps will kill just as certainly as the same bullet at 2,000 fps.
This cartridge in the game field is limited to 200 yards at most, and preferably 150 yards or less. Even with high-end loads it has the trajectory of a thrown grapefruit, compared to modern cartridges.
So there is little to be gained by increasing its velocity in the hope of flattening its trajectory.
Also, a 400 gr. bullet at 1,800 feet per second has heavy recoil. At 2,000 fps it must be brutal, especially from the Marlin 1895. The 1895 Cowboy with its longer and heavier barrel adds weight to the rifle, to help tame recoil, but it still must be stiff.
It is not my intent to rile gallatin but only to offer my experience in 27 years of shooting the Marlin 1895, and my opinions based upon that.
If you wish to hot-rod your Marlin with maximum loads, it's your choice. Your rifle will wear much quicker and there's always the chance it may be damaged, fed such a steady diet. You don't get something for nothing.
A 400 gr., .45-caliber bullet at 1,700 fps will take anything in North and South America. Shot placement is the deciding factor with a bullet this big and heavy, not increased velocity.
Interestingly, there are two calibers whose loads posted on the Internet often exceed the safe recommendations by modern reloading books: .45-70 and .45 Long Colt.
For whatever reason, though these rounds have been battle and field-tested as manstoppers and game-getters for more than 125 years, today's shooters seem to regard them as little more than "punkin' rollers."
The .45-70 killed moose, elk buffalo and grizzly for years with a 405 gr. lead bullet at 1,200 to 1,300 fps long before the word Magnum entered the shooting lexicon.