The 300 gr. bullet is designed for deer-sized animals with relatively thin skin. Don't ponder using it for elk, bear, moose or where a lot of penetration is needed.
I bought my Marlin 1895 in 1977. Been reloading for it since. It's a wonderful rifle but I would urge you to resist the temptation to Magnumize it with high-pressure loads.
Millions of deer, buffalo, bear, moose, elk and other critters have fallen to the old, .45-70 load of a 405 grain lead bullet at 1,250 feet per second, or thereabouts.
With a bullet this big, and this heavy, high velocity isn't needed to make a clean kill. What
is required is good bullet placement. Marksmanship cannot be substituted with velocity.
I would also urge you to view all loads on the internet suspiciously. I've seen loads posted for the 1895 Marlin that, if not gun-wreckers, were surely straining the gun so much that they were time bombs.
Why people have to eke the last few feet per seconds out of the .45-70, and strain their gun doing so, is beyond me.
These same maniacs would try to create +p loads for the Browning .50-cal for hunting chipmunks!
When I visit my cabin in British Columbia, Canada, I bring my Marlin 1895 loaded with the Lyman 457193 flatpoint cast bullet at about 1,600 fps. I have no doubts that it will protect me from any grizzly, black bear or moose that poses a danger. Boosting that same bullet to 1,800 fps causes fearsome recoil and may prevent me from getting a quick, second shot.
Okay, the ol' grumpy cat will get down off his soapbox.
As for using the 300 gr. jacketed bullet and IMR 4895:
Some folks on here have listed loads for Hodgdon 4895, not the IMR 4895 that you listed. Here's what the IMR Powder folks recommend for a 300 gr. jacketed bullet in lever-action .45-70 rifles:
Starting LoadBullet: 300 gr. jacketed HP
Bullet diameter: .458 inch
Powder: IMR 4895 - 58.5 grs.
Velocity: 1,800 fps
Pressure: 19,900 Copper Units of Pressure (CUP)
Overall Cartridge Length: 2.525 inch
Maximum LoadBullet: 300 gr. jacketed HP
Bullet diameter: 458 inch
Powder IMR 4895 - 65.0 grs. (Compressed Load)
Velocity: 2,087 fps
Pressure: 30,000 CUP
Overall Cartridge Length: 2.525 inch
Note: IMR 4895 and Hodgdon 4895 are NOT the same powders. Pay attention to this fact when researching loads. Both powders are now marketed by Hodgdon, and loads for both are listed separately on the Hodgdon website.
Also, pay particular attention to the overall cartridge length for your Marlin.
Original and reissued 1886 Winchesters will accommodate longer cartridges than the 1895 Marlin, so ensure you're not using an overall cartridge length suggested for the 1886 Winchester.
Loading an over-long cartridge into the Marlin will tie up the gun, requiring time and effort to remove it. Ample cussing is usually required too (the voice of experience here).
I don't use either 4895 in my own 45-70. IMR 3031 is one of the finest powders to use in this cartridge, when used in the Marlin. I've decided that the Maximum load in my own Marlin is 50.0 grains of IMR 3031 under the jacketed 400 to 405 gr. bullet. Any more than this, and tell-tale signs of too much pressure are evident.
The late Elmer Keith used to recommend 53.0 grs. of IMR 3031 for the 1886 Winchester, under a 405 gr. jacketed bullet, but that was more than 50 years ago. The volume of cases, primer strength (brisance) and IMR 3031 powder itself have changed slightly since Keith was reloading. Avoid his classic load.
The .45-70 is a very easy cartridge to load. It's accurate and incredibly versatile.
Down the road, if you get in a playful mood, you can load three .457 inch lead balls in a single case, for a multiple projectile load that's fun to shoot at close range.
Or you can create shotshells using .45-caliber felt Wonder Wads or gas checks, or a combination of both. These are good loads to have in your pocket if you're hunting and run across a grouse or rabbit at close range.
Seat a hollow-based, factory .45 Long Colt 250 gr. conical lead bullet in the .45-70 and you'll have a fun plinking and small game load.
A caseful of FFFG black powder and a couple of Wonder Wads seated firmly on top creates a good, booming blank for Fourth of July or New Year's Eve. Just remember to clean your rifle and the case right away, to avoid corrosion from the salts in black powder.
The .45-70 cartridge is a marvelous round. You're going to love it.
